Feel bitter about bank's research department (6)
I believe the answer is:
resent
'feel bitter' is the definition.
(I've seen this before)
'research department' is the wordplay.
'research' becomes 'res' (academic abbreviation).
'department' becomes 'ent' (I can't justify this - if you can you should believe this answer much more).
'res'+'ent'='RESENT'
'about bank's' acts as a link.
I am not very happy about this link. Some or all of it may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for resent that I've seen before include "Dispatched again - take amiss" , "Be offended by" , "Dispatched again; feel bitterness at" , "Enters (anag)" , "Consider (something) to be an affront" .)