Background for part of play on track (7)
I believe the answer is:
scenery
'background' is the definition.
(I've seen this before)
'part of play on track' is the wordplay.
'part of play' becomes 'scene' ('scene' is part of 'play').
'on' is a charade indicator (letters next to each other).
'track' becomes 'ry'.
'scene'+'ry'='SCENERY'
'for' is the link.
(Other definitions for scenery that I've seen before include "Stage sets" , "Landscape features" , "Picturesque view or stage dicor" , "movie sets?" , "Stage setting" .)