Not reversed to make weight (3)
I believe the answer is:
ton
'weight' is the definition.
(unit of weight)
'not reversed' is the wordplay.
'reversed' says the letters should be written backwards.
'not' reversed gives 'TON'.
'to make' acts as a link.
(Other definitions for ton that I've seen before include "Century" , "Two thousand - two hundred and forty pounds" , "Style" , "Heavyweight" , "Weight - fashion (French)" .)