Orioles regularly abandoned eggs (3)
I believe the answer is:
roe
'eggs' is the definition.
(fish eggs)
'orioles regularly abandoned' is the wordplay.
'regularly abandoned' indicates alternate letters (letters removed at regular intervals).
The alternating letters of 'orioles' are 'ROE'.
(Other definitions for roe that I've seen before include "A mass of fish-eggs" , "Lobster's ripe ovary" , "Hoofed animal(s)" , "Fish eggs; small deer" , "Mass of fish eggs" .)