(n.) One who defends; one who maintains, supports, protects, or vindicates; a champion; an advocate; a vindicator.

Maecenas abettor admirer advocate aficionado angel apologete apologist apologizer backer buff champion dependence encourager endorser exponent fan favorer friend at court guard justifier lover mainstay maintainer paladin paranymph partisan patron patroness pillar pleader promoter proponent protagonist protector protectress reliance rock safekeeper second seconder sectary sider sponsor stalwart standby successful advocate support supporter sustainer sympathizer tower tower of strength upholder vindicator votary well-wisher whitewasher