Man, say, bound to cut head (7)
I believe the answer is:
primate
'man say' is the definition.
(man is a kind of primate)
'bound to cut head' is the wordplay.
'bound' becomes 'rim' (both can mean a limit or boundary).
'to cut' is an insertion indicator (some letters cut their way into a word).
'head' becomes 'pate' (humorous term for the head).
'rim' inserted inside 'pate' is 'PRIMATE'.
(Other definitions for primate that I've seen before include "Chief priest" , "Mammal such as human" , "C of E archbishop" , "Higher mammal" , "senior clergyman" .)