Republican to employ stratagem (4)
I believe the answer is:
ruse
'stratagem' is the definition.
(I've seen this before)
'republican to employ' is the wordplay.
'republican' becomes 'r' (abbreviation).
'to employ' becomes 'use' ('use' can be a synonym of 'employ').
'r'+'use'='RUSE'
(Other definitions for ruse that I've seen before include "Deceptive manoeuvre" , "Sure its a strange deception" , "Trick designed to deceive" , "Clever stratagem or plan" , "Deceptive device" .)