toehold

noun3

1. •
   A foothold small enough to support just the toe.
2. •
   (figurative) 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. — 1990
3. •
   A hold in which the aggressor bends back the opponent's foot.