Cuts back on seconds and extras (6)
I believe the answer is:
spares
'extras' is the definition.
(both can mean leftovers)
'cuts back on seconds' is the wordplay.
'cuts back' becomes 'pares' (to pare is to trim or cut back).
'on' is a charade indicator (letters next to each other).
'seconds' becomes 's'.
'pares' after 's' is 'SPARES'.
'and' acts as a link.
(Other definitions for spares that I've seen before include "Lets off; reserve parts" , "Is merciful towards, refrains from hurting" , "Extras with spears" , "Extras in case of necessity" , "Replacement items, like tyres" .)