factor

ambassador, diplomat, diplomatist, emissary, foreign minister, legate, plenipotentiary

alternate, backup, pinch hitter, relief, replacement, stand-in, sub, substitute, surrogate, understudy

informer, operative, spy

broker, distributor, manager

arbiter, arbitrator, comprador (or compradore), conciliator, go-between, intercessor, intermediary, interposer, liaison, mediator, middleman, peacemaker

mouthpiece, point man, point person, prophet, speaker, spokesman, spokesperson

basis, part and parcel

detail, item, particular, point

aspect, characteristic, facet, feature, trait

division, fragment, particle, partition, piece, portion, section, sector, segment

subcomponent