Green piles of hay in lots of five lines? (9)
I believe the answer is:
limericks
'lots of five lines?' is the definition.
(a limerick is a poem of five lines)
'green piles' is the wordplay.
'green' becomes 'lime' (lime is a shade of green).
'piles' becomes 'ricks' (ricking is a kind of piling).
'lime'+'ricks'='LIMERICKS'
'of hay in' is the link.
I am not very happy about this link. Some or all of it may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for limericks that I've seen before include "Five-line verses" , "Five-lined verses" , "Humorous verses of 5 lines" .)