Golfer’s action to succeed with first two of three below par? (6-7)
I believe the answer is:
follow-through
'golfer's action' is the definition.
(continuing a stroke after hitting a golf ball)
'succeed with first two of three below par?' is the wordplay.
'succeed' becomes 'follow' (synonyms).
'with first two of three' becomes 'th' (I can't justify this - if you can you should believe this answer much more).
'below par?' becomes 'rough' (feeling below par can mean feeling rough or ill).
'follow'+'th'+'rough'='FOLLOW-THROUGH'
'to' acts as a link.
(Other definitions for follow-through that I've seen before include "Stroke's continuation" , "Part of stroke after ball has been hit" .)