Hit on including good hairstyle (7)
I believe the answer is:
chignon
'hairstyle' is the definition.
(chignon is a kind of hairstyle)
'hit on including good' is the wordplay.
'hit' becomes 'chin' (informal term meaning to punch someone's chin**).
'including' means one lot of letters goes inside another.
'good' becomes 'g' (abbreviation).
'chin'+'on'='chinon'
'chinon' enclosing 'g' is 'CHIGNON'.
(Other definitions for chignon that I've seen before include "Roll of hair worn at the nape" , "Topknot" , "Coil of hair at the back of the head" , "Arrangement of coil of hair" , "Hairstyle" .)