Leading lady cleared out in cunning fashion (6)
I believe the answer is:
archly
'in cunning fashion' is the definition.
'leading lady cleared out' is the wordplay.
'leading' becomes 'arch' (e.g. in arch-enemy).
'cleared out' means to remove the middle letters.
'lady' with its middle taken out is 'ly'.
'arch'+'ly'='ARCHLY'
(Other definitions for archly that I've seen before include "In a sly way" , "In a sly manner" , "In roguish manner" .)