This word is acceptable for play in the US & UK dictionaries that are being used in the following games:

• Lexulous
• Wordscraper
• Wordosaur

v. To loosen from a clenched position; relax: unclench one's fists.

verb-intransitive. To become unclenched.

v. to open (something that was clenched)

v. to relax, especially one's muscles

v. Same as unclinch.

To open, or to force open, as the closed hand.

"An Iranian theocratic regime had launched a bid for dominion in its region; Mr. Obama offered it an olive branch and waited for it to "unclench" its fist."

unclinch   

awkwardto    quivery    painful-looking    far-stretched    transmuting    paralyzed    vise-like    three-armed    whipcord    rag-doll