跨

Foot radical on the left — the indexing semantic. 跨 means to step over, straddle, cross. The 足 places the action squarely in the leg-and-foot family: 跑 (run), 跳 (jump), 踏 (tread), 跟 (follow at the heel), 越 (leap over). The radical pins 跨 as a foot-action, specifically a long stride.

Right component supplies the sound: kuā → kuà, just a tone shift. 夸 itself is 大 (large) over 亏 (used phonetically), giving an 'overlarge boast' image. The phonetic also pulls duty in 垮 kuǎ (collapse) and 挎 kuà (sling) — a tight kua family where the over-extension flavour shows through 跨's sense of stretching the legs across.