European mentioned part of fish (4)
I believe the answer is:
finn
'european' is the definition.
(Finn is an example)
'mentioned part of fish' is the wordplay.
'mentioned' indicates a 'sounds like' (homophone) clue.
'part of fish' becomes 'fin' ('fin' is part of 'fish').
'fin' sounds like 'FINN'.
(Other definitions for finn that I've seen before include "National" , "Eg, Helsinki native" , "hero of English or American novel" , "Northern European" , "Sibelius, perhaps" .)