toehold

A foothold small enough to support just the toe.

Any small advantage which allows one to make significant progress; a slight footing or foothold.

Were Herat to fall to the Persians, this would give the Russians a crucial and dangerous toe-hold in western Afghanistan.

The tiny old houses and flats of this once impoverished quarter had mostly been refurbished into toeholds for young Atlantans from all around the Anglosphere, poor in equity but rich in expectations, who had come to the great city to incubate their careers.

A hold in which the aggressor bends back the opponent's foot.