About to include clue - can't change unwillingness (10)
I believe the answer is:
reluctance
'unwillingness' is the definition.
(I know that reluctance is a type of unwillingness)
'about to include clue can't change' is the wordplay.
'about' becomes 're' ('re' means regarding or about).
'to include' means one lot of letters goes inside another.
'change' indicates anagramming the letters.
'clue'+'cant'='cluecant'
'cluecant' anagrammed gives 'eluctanc'.
're' going around 'eluctanc' is 'RELUCTANCE'.
(Other definitions for reluctance that I've seen before include "Wariness" , "averse reaction" , "Unwillingness (to do something)" , "Hesitation" .)