Rely on financial institution (4)
I believe the answer is:
bank
I believe this clue is a double definition.
'rely' is the first definition.
(thesaurus)
'financial institution' is the second definition.
(bank is a kind of financial institution)
'on' acts as a link.
(Other definitions for bank that I've seen before include "Sloping land" , "Long mound; rely (on)" , "store" , "River's edge" , "Financial institution - riverside" .)