Clumsily done, in my long poem (8)
I believe the answer is:
endymion
'long poem' is the definition.
The definition suggests a singular noun which matches the answer.
'clumsily done in my' is the wordplay.
'clumsily' indicates an anagram.
'done'+'in'+'my'='doneinmy'
'doneinmy' with letters rearranged gives 'ENDYMION'.
Can you help me to learn more?
(Other definitions for endymion that I've seen before include "Handsome shepherd of myth" , "story of Keats" , "Work by Keats" , "Moon lover; Keats poem" , "Poem by Keats; beautiful youth" .)