Five lines of green seen as superior to stack of hay (8)
I believe the answer is:
limerick
'five lines of' is the definition.
The definition suggests a singular noun which matches the answer.
'green seen as superior to stack of hay' is the wordplay.
I cannot quite understand how this works, but
'green' could be 'lime' (lime is a shade of green) and 'lime' is present in the answer.
'stack' could be 'rick' (rick is a kind of stack) and 'rick' is found in the answer.
No letters remain.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for limerick that I've seen before include "Irish county's produced" , "Type of humorous verse" , "Verse form - Irish city" , "Humorous five-line verse" , "[EDWARD LEAR] work" .)