Right oven should do this (5)
I believe the answer is:
roast
'should do this' is the definition.
The definition suggests a singular noun which matches the answer.
'right oven' is the wordplay.
'right' becomes 'r' (abbreviation).
'oven' becomes 'oast' (type of kiln).
'r'+'oast'='ROAST'
(Other definitions for roast that I've seen before include "Get very warm" , "Cooked joint" , "Cook (meat) over a fire" , "Grill" , "& 3 Accompaniment to Yorkshire pudding?" .)