Harsh routine involved in classical dance? Not half (6)
I believe the answer is:
brutal
'harsh' is the definition.
('brutal' can be a synonym of 'harsh')
'routine involved in classical dance? not half' is the wordplay.
'routine' becomes 'rut' (rut is a kind of routine).
'involved in' indicates putting letters inside.
'classical dance?' becomes 'ballet' (I've seen this before).
'not half' suggests halving the letters.
'ballet' cut in half is 'bal'.
'rut' placed within 'bal' is 'BRUTAL'.
(Other definitions for brutal that I've seen before include "Cruel, in animal fashion" , "Harsh, merciless" , "Vicious" , "Callous" , "Inhuman - pitiless" .)