Is and isn't improper to accept no refusal (6)
I believe the answer is:
insist
'accept no refusal' is the definition.
I can't tell whether this defines the answer.
'is and isn't improper' is the wordplay.
'and' is a charade indicator (letters next to each other).
'improper' indicates an anagram.
'is'+'isnt'='isisnt'
'isisnt' with letters rearranged gives 'INSIST'.
'to' is the link.
Can you help me to learn more?
(Other definitions for insist that I've seen before include "Maintain firmly" , "Continue to assert, maintain" , "Be adamant" , "Put one's foot down" , "Beg persistently and urgently" .)