Golfer's goal, they say, is complete (5)
I believe the answer is:
whole
'is complete' is the definition.
(associated in meaning)
'golfer's goal they say' is the wordplay.
'golfer's goal' becomes 'hole' (I've seen this in another clue).
'they say' shows a homophone (sound like).
'hole' sounds like 'WHOLE'.
(Other definitions for whole that I've seen before include "Integral" , "Total" , "Complete, containing all the parts" , "undamaged" , "Entire, undivided" .)