Refuse match with large harbour (5)
I believe the answer is:
filth
'refuse' is the definition.
(I've seen this in another clue)
'match with large harbour' is the wordplay.
I cannot quite understand how this works, but
'large' could be 'l' (eg in clothes sizes) and 'l' is located in the answer.
'match' could be 'fit' (synonyms) and 'fit' is present in the leftover letters.
A single letter 'h' 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?
(Other definitions for filth that I've seen before include "Dirt, obscene talk" , "Squalor" , "Real dirt or obscenity" , "Muck" , "Carrion" .)