Wearing nothing to protect onset of golfer’s elbow (5)
I believe the answer is:
nudge
'elbow' is the definition.
(synonyms)
'wearing nothing to protect onset of golfer's' is the wordplay.
'wearing nothing' becomes 'nude' (in the nude).
'to protect' is an insertion indicator.
'onset of' indicates taking the first letters.
The first letter of 'golfers' is 'g'.
'nude' placed around 'g' is 'NUDGE'.
(Other definitions for nudge that I've seen before include "Facility of pinball machine" , "Gentle encouragement" , "Gentle poke with elbow" , "Give a reminder" , "Remind (with the elbow?)" .)