Slough's fine, next to no-good part of the UK (7)
I believe the answer is:
fenland
'slough's' is the definition.
(thesaurus)
'fine next to no-good part of the uk' is the wordplay.
I cannot really understand how this works, but
'fine' could be 'f' (abbreviation) and 'f' is present in the answer.
'no' could be 'n' (common abbreviation y/n) and 'n' is found within the answer.
'part' could be 'land' (I have seen 'Part of Germany' mean 'land' so perhaps 'part' could also mean 'land') and 'land' is found within the answer.
A single letter 'e' remains which might be clued in a way I don't see.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Another definition for fenland that I've seen is " Marshy area".)