Hit golf ball badly over river, then withdrew (6)
I believe the answer is:
shrank
'withdrew' is the definition.
'hit golf ball badly over river' is the wordplay.
'hit golf ball badly' becomes 'shank'.
'over' indicates putting letters inside.
'river' becomes 'r'.
'shank' going around 'r' is 'SHRANK'.
'then' is the link.
(Other definitions for shrank that I've seen before include "Shrivelled" , "Contracted, grew smaller" , "Recoiled" , "Got less" , "Flinched" .)