Many first-time voters (5)
I believe the answer is:
teens
'many first-time voters' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for teens that I've seen before include "Between 12 and 20" , "Adolescence" , "The years 13 to 19" , "Years 13-19" , "13-19 age group" .)