Bank in quarrel yields (4)
I believe the answer is:
rely
'bank' is the definition.
(to bank on is to rely on)
'in quarrel yields' is the wordplay.
'in' indicates a hidden word.
'RELY' is hidden in the letters of 'quarrel yields'.
(Other definitions for rely that I've seen before include "Be sure" , "Depend (upon)" , "Depend, bank" , "Run and see" , "Count" .)