… show approval of credit (4)
I believe the answer is:
tick
This clue is a double definition.
'show approval of' is the first definition.
(giving a tick indicates approval)
'credit' is the second definition.
(I've seen this in other clues)
(Other definitions for tick that I've seen before include "Second" , "Check the small mattress?" , "Minute" , "Credit; clock sound" , "Moment; bloodsucker" .)