Stack is after one of The Greens in Munster (8)
I believe the answer is:
limerick
'munster' is the definition.
Both the definition and answer are singular nouns.
Maybe you can see a link between them that I can't see?
'stack is after one of the greens' is the wordplay.
'stack' becomes 'rick' (rick is a kind of stack).
'is after' says to put letters next to each other.
'one of the greens' becomes 'lime' (I can't explain this - if you can you should believe this answer much more).
'rick' after 'lime' is 'LIMERICK'.
'in' acts as a link.
Can you help me to learn more?
(Other definitions for limerick that I've seen before include "port used in Ireland" , "Humorous short poem" , "Witty poem from mid-western Irish city" , "Irish county - five-line poem" , "Five-lined poem" .)