One of eight born at the same time (8)
I believe the answer is:
octuplet
'one of eight born at the same time' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for octuplet that I've seen before include "One of eight in birth" , "One of eight born together" , "One of a group of eight children born at the same time" .)