They represent one convenience (6)
I believe the answer is:
agents
'they represent' is the definition.
The definition suggests an adverb but the answer is not.
'one convenience' is the wordplay.
'one' becomes 'a' (a thing is one thing).
'convenience' becomes 'gents' (I've seen this before).
'a'+'gents'='AGENTS'
Can you help me to learn more?
(Other definitions for agents that I've seen before include "Representatives" , "They act for actors" , "Instruments" , "Sales reps" , "travelling salesmen" .)