People rallying first competitor (5)
I believe the answer is:
racer
'competitor' is the definition.
(someone competing in a race)
'people rallying first' is the wordplay.
'people' becomes 'race' (people can mean a national group or race).
'rallying first' becomes 'r' (1st letter of 'rallying').
'race'+'r'='RACER'
(Other definitions for racer that I've seen before include "Bike, perhaps" , "Speedway competitor, perhaps" , "American snake" , "Perhaps 16 [SCRAMBLER]" , "Fast driver" .)