Refusal, in any case, to be a nuisance (5)
I believe the answer is:
annoy
'to be a nuisance' is the definition.
(I've seen this before)
'refusal in any' is the wordplay.
'refusal' becomes 'no' (saying no to something).
'in' indicates putting letters inside.
'no' going into 'any' is 'ANNOY'.
'case' is the link.
I am not very happy about this link. It may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for annoy that I've seen before include "get angry" , "Displease" , "be a nuisance" , "eat" , "trouble" .)