Practice acting in Winter's Tale, initially (4)
I believe the answer is:
wont
'practice' is the definition.
(I know that wont is a type of custom)
'acting in winter's tale initially' is the wordplay.
'acting' becomes 'on' (I've seen this in other clues).
'in' means one lot of letters goes inside another.
'initially' indicates taking the first letters.
The first letters of 'winters tale' is 'wt'.
'on' going into 'wt' is 'WONT'.
(Other definitions for wont that I've seen before include "Is not going to" , "Accustomed" , "Habit" , "Succinct refusal" , "normal practice" .)