Steal from popular boy (5)
I believe the answer is:
robin
'boy' is the definition.
(I've seen this before)
'steal from popular' is the wordplay.
'steal from' becomes 'rob' (I've seen this before).
'popular' becomes 'in'.
'rob'+'in'='ROBIN'
(Other definitions for robin that I've seen before include "boy" , "Small songbird" , "Red-breasted songbird" , "See 12" , "Batman's helper" .)