Vier

6 clues
Rival
Contender
Contestant
Challenger
Competitor
One in a heat
Similar answers:
2layer
Aaaadvisor
Aaabattery
Aaamember
Aaapaper
Aabatteries
Aabattery
Aamember
Aamemberprofile
Aareaditalaeaer
Aaroncarter
Aasifmandvi
Aattheopera
Aattheraces
Aaverage
Aaverages
Abagofnerves
Abardseyeview
Abaser
Abasers