Bank subsidiary (4)
I believe the answer is:
side
I believe this clue is a double definition.
'bank' is the first definition.
(synonyms)
'subsidiary' is the second definition.
(thesaurus)
(Other definitions for side that I've seen before include "Wolves, say" , "long forgotten" , "Pomposity - bias - team" , "Sporting team" , "Football team" .)