Gruesome barber occasionally going into club (7)
I believe the answer is:
macabre
'gruesome' is the definition.
(both can mean morbid or disturbing)
'barber occasionally going into club' is the wordplay.
'occasionally' means one should take alternating letters (letters taken at regular intervals or occasions).
'going into' indicates putting letters inside.
'club' becomes 'mace' (mace can mean a club or stick).
The alternate letters of 'barber' are 'abr'.
'abr' going inside 'mace' is 'MACABRE'.
(Other definitions for macabre that I've seen before include "Gruesome, morbid" , "Ghastly, gruesome" , "Dark and disturbing" , "Chilling" , "Grotesque" .)