Ring in schedule for early-morning caller (7)
I believe the answer is:
rooster
'early-morning caller' is the definition.
(bird which makes a call early in the morning)
'ring in schedule' is the wordplay.
'ring' becomes 'o' (letter resembling a ring).
'in' is an insertion indicator.
'schedule' becomes 'roster' (I've seen this before).
'o' placed inside 'roster' is 'ROOSTER'.
'for' acts as a link.
(Other definitions for rooster that I've seen before include "8 [RURAL] alarm call" , "Farmyard fowl" , "Bird that wakes up" , "One may crow" , "Morning caller" .)