Banks perhaps aim to maintain excellent rates in the first instance (10)
I believe the answer is:
goalkeeper
'rates in the first instance' is the definition.
Although both the answer and definition are singular nouns, I don't see how they can define each other.
'banks perhaps aim to maintain excellent' is the wordplay.
I cannot quite see how this works, but
'aim' could be 'goal' (I've seen this before) and 'goal' is found in the answer.
'maintain' could be 'keep' (synonyms) and 'keep' is found in the answer.
The remaining letters 'er' is a valid word which might be clued in a way I don't see.
This may be the basis of clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for goalkeeper that I've seen before include "Seaman was one" , "Given one of these" , "A Greek pole (anag.)" , "Given, say" .)