Set piece player involved in scrum (4)
I believe the answer is:
prop
I believe this is a double definition.
'set piece' is the first definition.
(I've seen this in another clue)
'player involved in scrum' is the second definition.
(I've seen this before)
(Other definitions for prop that I've seen before include "player involved in scrum" , "Support; object used on stage" , "A rigid support - 37 Across is one" , "See 5" , "Object used on the set of a play" .)