One often paying a fee (4)
I believe the answer is:
user
'one often paying a fee' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for user that I've seen before include "With 1a [NEW] he'll need different login" , "Person employing something" , "One who employs" , "One who works an appliance" , "Operator; exploiter" .)