Spies in a public convenience (6)
I believe the answer is:
agents
'spies' is the definition.
(I've seen this before)
'a public convenience' is the wordplay.
'public convenience' becomes 'gents' (I've seen this before).
'a'+'gents'='AGENTS'
'in' acts as a link.
(Other definitions for agents that I've seen before include "They act for others" , "Sales reps" , "They do business on behalf of others" , "They act for actors" , "Instruments" .)