Joint group of players turned over (5)
I believe the answer is:
tenon
'joint' is the definition.
(I've seen this before)
'group of players turned over' is the wordplay.
'group of players' becomes 'nonet' (I've seen this before).
'turned over' says the letters should be written in reverse.
'nonet' written backwards gives 'TENON'.
(Other definitions for tenon that I've seen before include "Part of joint that fits in mortise" , "Mortise counterpart" , "Wood fitting into a mortise" , "Piece of wood fitting into a mortice" , "Type of small saw" .)