Leave to play top side (7)
I believe the answer is:
deposit
'leave' is the definition.
(I've seen this before)
'play top side' is the wordplay.
'play' is an anagram indicator.
'top side' becomes 'topside' (synonyms).
'topside' with letters rearranged gives 'DEPOSIT'.
'to' acts as a link.
(Other definitions for deposit that I've seen before include "is one back on the bottle?" , "Down-payment" , "Drop" , "Returnable sum" , "Money up front" .)