Employed when previously owned (4)
I believe the answer is:
used
I believe this clue is a double definition.
'employed' is the first definition.
('use' can be a synonym of 'employ')
'previously owned' is the second definition.
(I've seen this in another clue)
'when' acts as a link.
(Other definitions for used that I've seen before include "Availed oneself of" , "Took advantage of" , "Put to a purpose" , "Second hand" , "Second-hand; consumed" .)