The cold leg I carved before dinner started (5)
I believe the answer is:
gelid
'the cold' is the definition.
(thesaurus)
'leg i carved before dinner started' is the wordplay.
'carved' indicates an anagram.
'before' says to put letters next to each other.
'started' indicates taking the first letters.
The first letter of 'dinner' is 'd'.
'leg'+'i'='legi'
'legi' anagrammed gives 'geli'.
'geli'+'d'='GELID'
(Other definitions for gelid that I've seen before include "Extremely cold, frozen" , "Glacial" , "Icy cold - glide (anag)" .)