In revolt, blocking head's move to new form (6)
I believe the answer is:
pupate
'move to new form' is the definition.
'in revolt blocking head's' is the wordplay.
'in revolt' becomes 'up' (I've seen this in other clues).
'blocking' indicates putting letters inside.
'head' becomes 'pate' (I've seen this before).
'up' placed into 'pate' is 'PUPATE'.
(Other definitions for pupate that I've seen before include "What insects do" , "Change into a chrysalis" , "Turn into a chrysalis" , "Become a chrysalis" , "To develop biologically" .)