Put back boy's hat (7)
I believe the answer is:
stetson
'hat' is the definition.
(Stetson is an example)
'put back boy's' is the wordplay.
'put back' becomes 'stet' (I've seen this in other clues).
'boy' becomes 'son' ('son' can be a synonym of 'boy'**).
'stet'+'son'='STETSON'
(Other definitions for stetson that I've seen before include "Capital investment" , "Tip" , "St Neots (anag.)" , "Hat, for Texan oil magnate, say" , "Hat with wide brim and high crown, maybe a cowboy's" .)