Credit note covers removal of fat that sits at the neck (4-2)
I believe the answer is:
clip-on
'fat that sits at the neck' is the definition.
Both the definition and answer are adjectives. Maybe you can see an association between them that I can't see?
'credit note covers removal of' is the wordplay.
I cannot really see how this works, but
'note' could be 'n' (abbreviation) and 'n' is found within the answer.
'of' could be 'o' and 'o' is located in the answer.
The remaining letters 'clip' is a valid word 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 clip-on that I've seen before include "Easily removable tie" , "Attachable" , "Kind or earring or bow tie" , "Like some ties" , "Attached like a bow tie, for example" .)