standby

Noun	1.	standby - something that can be relied on when needed
	2.	standby - an actor able to replace a regular performer when required Synonyms: understudy
Adj.	1.	standby - ready for emergency use; "a standby generator"; "a standby crew"

Maecenas, abettor, admirer, advocate, aficionado, angel, apologist, backer, bit player, buff, champion, defender, dependence, encourager, endorser, exponent, extra, fan, favorer, figurant, figurante, friend at court, lover, mainstay, maintainer, mute, paranymph, partisan, patron, promoter, protagonist, reliance, second, seconder, sectary, sider, spear-carrier, sponsor, stalwart, stand-in, substitute, supe, super, supernumerary, support, supporter, supporting actor, supporting cast, sustainer, sympathizer, understudy, upholder, votary, walk-on, walking gentleman, well-wisher