Scrap and win, boxing clever, finally (5)
I believe the answer is:
grain
'scrap' is the definition.
(thesaurus)
'win boxing clever finally' is the wordplay.
'win' becomes 'gain' ('gain' can be a synonym of 'win'**).
'boxing' indicates putting letters inside ('box' can mean contain, as in to put in a box).
'finally' suggests the final letters.
The final letter of 'clever' is 'r'.
'gain' placed around 'r' is 'GRAIN'.
'and' acts as a link.
(Other definitions for grain that I've seen before include "Cereal as food" , "Small hard particle of anything" , "Enter into combat with" , "Small quantity (of corn etc)" , "Cereal seed" .)