Cold scrap of food scoffed by Welshman: then seconds (11)
I believe the answer is:
remorseless
'cold' is the definition.
'scrap of food scoffed by welshman then seconds' is the wordplay.
'scrap of food' becomes 'morsel' (I've seen this before).
'scoffed by' means one lot of letters goes inside another (scoff can mean to eat or consume).
'welshman' becomes 'rees' (I've seen this in other clues).
'then' means one lot of letters go next to another.
'seconds' becomes 's'.
'morsel' inserted into 'rees' is 'remorseles'.
'remorseles'+'s'='REMORSELESS'
(Other definitions for remorseless that I've seen before include "Unrelenting" , "Cruel; without respite" , "Lacking compassion" , "Without regret or guilt" , "Not letting up," .)