Subscriber (6)
I believe the answer is:
reader
'subscriber' is the definition.
(I know that subscriber can be written as reader)
This is all the clue.
(Other definitions for reader that I've seen before include "See 15" , "He's immersed in a book or newspaper" , "University lecturer, ranking below a professor" , "Person perusing a book or newspaper" , "Peruser, of books perhaps" .)