Earthly enrichment a chap can possibly rue? (6)
I believe the answer is:
manure
'earthly enrichment' is the definition.
Although both the answer and definition are singular nouns, I don't see how one could define the other.
'a chap can possibly rue?' is the wordplay.
'a chap can' becomes 'man' (I can't justify this - if you can you should believe this answer much more).
'possibly' indicates an anagram.
'rue' anagrammed gives 'ure'.
'man'+'ure'='MANURE'
Can you help me to learn more?
(Other definitions for manure that I've seen before include "Organic fertiliser" , "Animal excreta as fertiliser" , "should promote growth" , "Animal excreta used to fertilise land" , "Crap" .)