strangle
縊 centers on the act of strangling, specifically by tightening a cord or rope around the neck.
縊 combines 糸 (thread/cord) with 益, which likely contributes the sound. The character suggests strangling with a cord.
The left side 糸 is a thread or cord, and the right side 益 looks like a vessel with a lid. Picture a cord tightening around a neck like a lid sealing a vessel.
For イ, imagine the sound of a cord pulled tight: 'ee' as it strangles. The 'ee' sound cues イ.