Aware of refusal to enter when kit's off (2,3,4)
I believe the answer is:
in the know
'aware of' is the definition.
(I've seen this before)
'refusal to enter when kit's off' is the wordplay.
'refusal' becomes 'no'.
'to enter' indicates putting letters inside.
'off' indicates anagramming the letters.
'when'+'kit'='whenkit'
'whenkit' is an anagram of 'inthekw'.
'no' placed into 'inthekw' is 'IN THE KNOW'.
(Other definitions for in the know that I've seen before include "well-informed" , "Having been informed" , "Privy to special information" , "Aware" , "Informally, having inside information" .)