In a similar manner to a sidekick, the back-kick supports a hero or superhero in his (or her) endeavors. The difference arises in that a back-kick provides support from an external area, (hideout, lair, rooftop, etc.), usually through Intel, weapons, and vehicles. The back-kick's duties may extend into general maintenance of the hero's hideout (bitchwork), or in some cases, emotional support.
Alfred Pennyworth (of Batman) is a classic, well-known example of a back-kick.