Stratagem or trick (4)
I believe the answer is:
ruse
This clue is a double definition.
'stratagem' is the first definition.
(a ruse is a stratagem or ploy)
'trick' is the second definition.
(I've seen this in other clues)
(Other definitions for ruse that I've seen before include "Cunning scheme" , "Deceptive device" , "Ploy, artifice" , "Trick, stratagem" , "Sure to be a trick" .)