Eccentric rodent-catcher might use it! (6)
I believe the answer is:
ratbag
'eccentric' is the definition.
Both the definition and answer are singular nouns.
Perhaps you can see an association between them that I can't see?
'rodent-catcher might use it' is the wordplay.
I cannot quite see how this works, but
'rodent' could be 'rat' (rat is a kind of rodent) and 'rat' is located in the answer.
The remaining letters 'bag' is a valid word which might be clued in a way I don't see.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for ratbag that I've seen before include "One displaying bad form" , "Grab at (anag) - contemptible person" , "bounder" , "unpleasant customer" , "snake" .)