Call for quiet time (4)
I believe the answer is:
page
'call for' is the definition.
(to page is to call with a pager)
'quiet time' is the wordplay.
'quiet' becomes 'p' (music symbol for 'piano', ie soft or quiet).
'time' becomes 'age' (an age is a period of time).
'p'+'age'='PAGE'
(Other definitions for page that I've seen before include "Section of biography perhaps" , "Attendant - this is on one!" , "Leaf of book etc" , "one seeking knighthood" , "Boy at wedding" .)