Daily item on sale for scheduled period (4,4)
I believe the answer is:
time slot
'scheduled period' is the definition.
(a particular period of time)
'daily item on sale' is the wordplay.
'daily' becomes 'times' (daily UK newspaper).
'item on sale' becomes 'lot' (as in lots at an auction).
'times'+'lot'='TIME SLOT'
'for' acts as a link.
(Other definitions for time slot that I've seen before include "Specified interval" , "Schedule period allocated to programme" , "limited period" , "It can be scheduled" .)