Balding slim leg-spinner (4,2,3)
I believe the answer is:
thin on top
'balding' is the definition.
(I've seen this before)
'slim leg-spinner' is the wordplay.
'slim' becomes 'thin' ('thin' can be similar in meaning to 'slim').
'leg' becomes 'on' (cricket term, fielding positions).
'spinner' becomes 'top' (something that spins).
'thin'+'on'+'top'='THIN ON TOP'
(Other definitions for thin on top that I've seen before include "not so hairy now" , "showing scalp?" , "State of advancing baldness" , "developing a shine for the Head?" , "Going bald" .)