Cop and sailor fighting for citadel (9)
I believe the answer is:
acropolis
'for citadel' is the definition.
(acropolis is a kind of citadel)
'cop and sailor fighting' is the wordplay.
'and' is a charade indicator (letters next to each other).
'fighting' is an anagram indicator (I've seen this in other clues).
'cop' after 'sailor' is 'sailorcop'.
'sailorcop' with letters rearranged gives 'ACROPOLIS'.
(Other definitions for acropolis that I've seen before include "Imposing building" , "old citadel" , "Citadel of ancient Greece" , "Athenian landmark" , "Upper fortified part of Greek city as in Athens" .)