Use space and stratagem (6)
I believe the answer is:
employ
'use' is the definition.
('employ' can be a synonym of 'use')
'space and stratagem' is the wordplay.
'space' becomes 'em' (in typography, a space as wide as a letter 'm').
'and' says to put letters next to each other.
'stratagem' becomes 'ploy' ('ploy' can be a synonym of 'stratagem').
'em'+'ploy'='EMPLOY'
(Other definitions for employ that I've seen before include "Give job to (someone)" , "Hire; use" , "Use or give job to" , "Put on the payroll" , "Give work to (person)" .)