Spies a convenience (6)

I believe the answer is:

agents

'spies' is the definition.
(I've seen this before)

'a convenience' is the wordplay.
'convenience' becomes 'gents' (I've seen this before).
'a'+'gents'='AGENTS'

(Other definitions for agents that I've seen before include "Spies" , "They act for actors" , "travelling salesmen" , "They act for others" , "Factors" .)

I've seen this clue in The Telegraph.

Want a hint initially instead of a full solution? Install my app