They employ clever ruses (5)
I believe the answer is:
users
'they employ' is the definition.
(I've seen this in another clue)
'clever ruses' is the wordplay.
'clever' indicates anagramming the letters.
'ruses' anagrammed gives 'USERS'.
(Other definitions for users that I've seen before include "subscribers" , "Ruses for employers" , "Customers" , "People who take drugs" , "People with a drug habit" .)