Mustn’t hope for me to change ad hoc (4,2,3,6)
I believe the answer is:
spur of the moment
'ad hoc' is the definition.
Both the definition and answer are adjectives. Maybe you can see a link between them that I don't see?
'mustn't hope for me to change' is the wordplay.
'to change' is an anagram indicator.
'mustnt'+'hope'+'for'+'me'='mustnthopeforme'
'mustnthopeforme' with letters rearranged gives 'SPUR-OF-THE-MOMENT'.
Can you help me to learn more?
(Other definitions for spur of the moment that I've seen before include "Unplanned" , "Impulsive" , "in-form player at White Hart Lane?" , "Possibly Gareth Bale" , "impulse?" .)