悍

Left heart radical - the side-form of 心. The indexing radical, files 悍 in the family of temperament/feeling chars: 怕 fear, 怒 anger, 愤 indignation, 忱 sincerity. Marks 悍 as a character trait of the heart - fierceness, boldness, hot-tempered courage, the inner fire that drives a brave or violent person.

Right 旱 supplies the sound - hàn exactly, no shift. Pure phonetic role; the 'drought' meaning contributes only a faint metaphor of harsh dry heat that fits a fierce temperament. Same phonetic family: 汗 sweat, 捍 defend, 焊 weld, 翰 brush. The pairing of heart + heat-of-drought is a useful mnemonic - a parched, burning heart is one quick to anger.