Demographic group (6)
I believe the answer is:
cohort
'demographic group' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for cohort that I've seen before include "team of soldiers" , "Sidekick" , "Fighting band; part of Roman legion" , "One tenth of a Roman legion" , "One-tenth of a Roman legion, or a group of people" .)