Hermeneutics is about the principles of interpretation. It is an art as well as a science, because it is ultimately about people and how they understand things.
Tradition is how the Church has understood Scripture through the centuries. How the Church approaches Scripture has been subject to historical development concerning the canon of Scripture, the various manuscripts of Scripture, the principles by which the Church has interpreted Scripture, and the doctrines derived by the Church from Scripture. It is an ongoing conversation, with contributions from different ecclesiastical perspectives, different sets of hermeneutical principles, and different approaches concerning the intent of the human authors, intent of the divine author, reader perspectives, application as meaning, embracing theological interpretations of Scripture, and a variety of other considerations.
There is a sea of things to think about with all this, too much to explore in one lifetime, much less in one blog post. But if we develop a good historical understanding about the depth and breadth of the Tradition, it will help keep us from being insulated and isolated islands with provincial, or even ghettoized, mindsets when we come to The Book.
The question is not whether we should give place to tradition in our reading of Scripture. We already do, and it can no more be avoided than a fish can avoid the water it swims in. Even in our hermeneutics, we follow a tradition of how we ought to interpret. Hermeneutics has developed in the Church over the centuries, shifting in different directions and emphases at different times and places, and not everyone shares the same set of interpretive principles. The Reformers, for example, shifted in a particular interpretive direction, and if we follow in that direction, we are nonetheless following a hermeneutical tradition (and even that tradition has split off into other traditions in the years since the Reformation). So, the question of what sort of hermeneutics we should use is itself a continuing conversation in the Church.
The apostle Jude spoke about the faith which was once for all delivered, entrusted, handed down, to the saints (Jude 3). The content of that faith does not change. However, to receive that apostolic tradition does not mean that there is has never been or will be any development. For not everything that can be rightfully said about the apostolic faith has necessarily already been said. There may be more that is yet to be learned and understood from it.
The apostles would rightly warn us against such developments that would take us away from Christ and the gospel. But the difference is between doctrine that develops from and within the apostolic tradition, and is in agreement with Scripture, and doctrine that develops in addition to the apostolic tradition and is contrary to Scripture. The former would be in alignment with the gospel and the latter out of alignment with the gospel.
How the Church has come to articulate the doctrine of the Trinity is an example of the former. The Trinity is inherent in the Scriptures, though not explicitly stated. The particular way we think and speak of it in the Church today is a doctrinal development. It was not a new doctrine, but a historical development in our understanding of what was inherent in the Scriptures and the apostolic tradition. Even so, the council of Nicea did not explain for us the mystery of the Trinity. Rather, it preserved the mystery for us, leaving us safe boundaries within which to think and talk about it and still remain true to the testimony of the Scriptures and the witness of the apostles.
Likewise the hypostatic union — Jesus, fully divine and fully human. That has some serious implications about Mary — from whom Jesus received His humanity — such that she can rightfully be called Theotokos. This union of divinity and humanity in Christ has all sorts of implications, which the Church continues to explore, even after 2000 years.
There is much to be unpacked — about God, Christ, the Spirit, the gospel — certainly a lifetime's worth. The apostles did not necessarily work out for us all the implications of Christ and the gospel, and it is a very fertile field. God is infinite, and it would take an eternity to explore the divine interaction within the Godhead — and I expect that is what we will do as we enjoy eternal fellowship with the Father, Son and the Holy Spirit.
(See also Reading Scripture with the Church)