Gym compartment (6)
I believe the answer is:
locker
'gym compartment' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for locker that I've seen before include "Small compartment where things can be securely stored" , "Box" , "Storage unit for personal possessions" , "Store for personal possessions" , "Storage compartment" .)