Chopped liver and last of gravy? Certainly (6)
I believe the answer is:
verily
'certainly' is the definition.
(thesaurus)
'chopped liver and last of gravy?' is the wordplay.
'chopped' indicates anagramming the letters (letters chopped or smashed up).
'and' says to put letters next to each other.
'last of' says to take the final letters.
The final letter of 'gravy' is 'y'.
'liver' is an anagram of 'veril'.
'veril'+'y'='VERILY'
(Other definitions for verily that I've seen before include "It's livery, in truth" , "Truly (archaic)" .)