IPA: /ʌnˈklɛnʧ/
KK: /ʌnˈklɛnʧ/
To relax or release something that was tightly held or clenched.
After a long day, I finally managed to unclench my fists and relax.
Unclench → It is formed from "un-" (meaning not or opposite of) and "clench" (from Old English "clencan", meaning to grasp or hold tightly). The word "unclench" means to release or stop holding tightly.
Think of 'not' or 'opposite' ('un-') of 'grasping tightly' ('clench') — that's why unclench means to let go or release.