Standard piece of apparatus (3)
I believe the answer is:
par
'standard' is the definition.
(standard of play in golf)
'piece of apparatus' is the wordplay.
'piece of' indicates a hidden word.
'PAR' is hidden in the letters of 'apparatus'.
(Other definitions for par that I've seen before include "A number of golfing" , "Regular score" , "Face value; equal standing" , "Expected number of strokes for hole (golf)" , "Standard number of strokes for a golf-hole" .)