Friend put down small carpet in gym (8)
I believe the answer is:
playmate
'friend' is the definition.
(I know that Playmate is a type of associate)
'put down small carpet in gym' is the wordplay.
'put down' becomes 'lay' (lay something down).
'small carpet' becomes 'mat' (I've seen this before).
'in' is an insertion indicator.
'gym' becomes 'pe' (short for Physical Education).
'lay'+'mat'='laymat'
'laymat' going within 'pe' is 'PLAYMATE'.
(Other definitions for playmate that I've seen before include "fun chum" , "Companion for fun" , "Child's companion" , "Game participant" , "Recreational friend" .)