Brilliant stroke, working to get voucher (6)
I believe the answer is:
coupon
'voucher' is the definition.
(I know that voucher can be written as coupon)
'brilliant stroke working' is the wordplay.
'brilliant stroke' becomes 'coup' (I've seen this before).
'working' becomes 'on' (on can mean working or activated).
'coup'+'on'='COUPON'
'to get' acts as a link.
(Other definitions for coupon that I've seen before include "means to buy goods" , "betting slip" , "Voucher or ticket" , "Entry form" , "Token" .)