By which to win at whist? (8)
I believe the answer is:
trickery
'whist?' is the definition.
The answer and definition can be both acts as well as being singular nouns.
Maybe you can see a link between them that I can't see?
I don't understand the rest of the clue.
Can you help me to learn more?
(Other definitions for trickery that I've seen before include "Legerdemain" , "Cunning deceit" , "Practice of deception" , "Hocus-pocus" , "Smoke and mirrors?" .)