noun

a person who defends someone or something.

a determined defender of British interests

protector,guard,guardian,preserver,bodyguard,custodian,watchdog,keeper,overseer,superintendent,caretaker,steward,trustee,supporter,upholder,backer,champion,advocate,endorser,sustainer,bolsterer,apologist,proponent,exponent,promoter,apostle,standard-bearer,torchbearer,flagbearer,adherent,believer