A regret about golf dispute (5)
I believe the answer is:
argue
'dispute' is the definition.
(to argue something is to dispute or contest it)
'a regret about golf' is the wordplay.
'regret' becomes 'rue' (to rue something is to regret it).
'about' is an insertion indicator.
'golf' becomes 'g' (phonetic alphabet: alpha, bravo, charlie etc.).
'rue' enclosing 'g' is 'rgue'.
'a'+'rgue'='ARGUE'
(Other definitions for argue that I've seen before include "Debate, contest verbally" , "contradict" , "Squabble" , "Contend with reasoning" , "express disagreement" .)