Cooked greens, in the main, rolled around in relish (9)
I believe the answer is:
eagerness
'relish' is the definition.
(thesaurus)
'cooked greens in the main rolled around' is the wordplay.
'cooked' indicates an anagram (letters cooked into a new form).
'in the main' becomes 'sae' (I can't explain this - if you can you should give a lot more credence to this answer).
'rolled' says the letters should be written in reverse (letters roll back).
'around' is an insertion indicator.
'sae' in reverse letter order is 'eas'.
'greens' anagrammed gives 'gernes'.
'gernes' placed into 'eas' is 'EAGERNESS'.
'in' acts as a link.
Can you help me to learn more?
(Other definitions for eagerness that I've seen before include "'Keenness, avidness (9)'" , "Sense rage (anag.)" , "Avidity" , "Keenness, enthusiasm" , "Keen interest" .)