For instance, certainly not turning over what should be cooled before serving? (7)
I believe the answer is:
revenge
'over what should be cooled before serving?' is the definition.
I can't tell whether this defines the answer.
'for instance certainly not turning' is the wordplay.
'for instance' becomes 'eg' (synonyms).
'certainly not' becomes 'never' (I can't justify this - if you can you should give a lot more credence to this answer).
'turning' shows that the letters should be reversed in order.
'eg'+'never'='egnever'
'egnever' in reverse letter order is 'REVENGE'.
Can you help me to learn more?
(Other definitions for revenge that I've seen before include "Malicious retaliation" , "Ship remembered in verse" , "Retribution" , "An eye for an eye" , "Satisfaction taken for injury" .)