Beep on a beeper (4)
I believe the answer is:
page
'beep on a beeper' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for page that I've seen before include "a significant bit of history?" , "Young attendant for part of a book" , "contribution to book?" , "Section of biography perhaps" , "one seeking knighthood" .)