Rule to check about golf (5)
I believe the answer is:
reign
'rule' is the definition.
(reign is a kind of rule)
'check about golf' is the wordplay.
'check' becomes 'rein' (both can mean to control or limit**).
'about' means one lot of letters goes inside another.
'golf' becomes 'g' (phonetic alphabet: alpha, bravo, charlie etc.).
'rein' enclosing 'g' is 'REIGN'.
'to' acts as a link.
(Other definitions for reign that I've seen before include "Rule of monarch" , "Occupy the throne" , "Be champion" , "Monarch's time in the job" , "Predominance" .)