Agonist

5 clues
One struggling
One in a conflict
Contracting muscle
Competitor or contestant
Participant in a struggle
Similar answers:
Aagonizes
Abagofnerves
Abstractionist
Abstractionists
Accompanist
Adayago
Administer
Administerrites
Administers
Administershots
Administration
Administrator
Advicecolumnist
Afghanistan
Afghanistangetz
Agesago
Ago
Agoal
Agoat
Agob