Reheated meat dish: hot remains (4)
I believe the answer is:
hash
'reheated meat dish' is the definition.
(dish made from recooked meat)
'hot remains' is the wordplay.
'hot' becomes 'h' (common abbreviation eg on taps).
'remains' becomes 'ash' (remains of a fire).
'h'+'ash'='HASH'
(Other definitions for hash that I've seen before include "meat and potato dish" , "Complete mess" , "Recycled food" , "Mess; symbol" , "dish of meat and vegetables" .)