In the oven cut up, sir, melting, or rendering (7)
I believe the answer is:
version
'rendering' is the definition.
(I've seen this before)
'in the oven cut up sir melting' is the wordplay.
'in the' means one lot of letters goes inside another.
'cut up' indicates anagramming the letters.
'melting' indicates an anagram.
'oven' is an anagram of 'veon'.
'sir' is an anagram of 'rsi'.
'veon' placed around 'rsi' is 'VERSION'.
'or' acts as a link.
(Other definitions for version that I've seen before include "Account from one point of view" , "Sort" , "Rendition" , "Particular account of a matter" , "Something a little different - so riven (anag)" .)