Ray's gymnastic apparatus (4)
I believe the answer is:
beam
I believe this clue is a double definition.
'ray's' is the first definition.
(synonyms)
'gymnastic apparatus' is the second definition.
(I know that beam is a type of gymnastic apparatus)
(Other definitions for beam that I've seen before include "Smile, transmit (radio signal)" , "Smile broadly; plank" , "Big smile; ray" , "Ray - large piece of wood" , "Smile; piece of timber" .)