Standing a round for a crony (3)
I believe the answer is:
pal
'for a crony' is the definition.
('pal' can be a synonym of 'crony')
'standing a round' is the wordplay.
'standing' is a reversal indicator (in a down clue, letters stand up).
'a round' becomes 'lap' (as in a round or lap of a park).
'lap' reversed gives 'PAL'.
(Other definitions for pal that I've seen before include "Mate, buddy" , "China" , "Friend (colloq.)" , "Buddy, chum" , "Close friend" .)