Actors eat first in this social group (5)
I believe the answer is:
caste
'this social group' is the definition.
(I've seen this before)
'actors eat first' is the wordplay.
'actors' becomes 'cast' (group of actors).
'eat first' becomes 'e' (1st letter of 'eat').
'cast'+'e'='CASTE'
'in' acts as a link.
(Other definitions for caste that I've seen before include "Persons with class" , "Social class in Hinduism" , "Social system" , "Social station" , "A sect (anag)" .)