Cut up during your old treatment (7)
I believe the answer is:
therapy
'treatment' is the definition.
('therapy' can be a synonym of 'treatment')
'cut up during your old' is the wordplay.
'cut' becomes 'pare' (I've seen this before**).
'up' is a reversal indicator (in down clue: letters go upwards).
'during' is an insertion indicator.
'your old' becomes 'thy'.
'pare' written backwards gives 'erap'.
'erap' placed inside 'thy' is 'THERAPY'.
(Other definitions for therapy that I've seen before include "healing process" , "Medical treatment" , "Relieving treatment" , "Curative treatment" , "See 7" .)