Keyboard user (6)
I believe the answer is:
typist
'keyboard user' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for typist that I've seen before include "Operator of a machine that prints one character at a time" , "Person at keyboard" , "The old-style secretary, for one" , "Worker taken from pool, perhaps" , "Keyboard operator" .)