Unclench

Verb

 * 1)  to open (something) that was clenched
 * The baby stopped crying and unclenched her fists.
 * 1)  to relax, especially one's muscles
 * Bill, take some deep breaths and unclench.

Thesaurus
bare, clear, deobstruct, disclose, expose, free, manifest, patefy, reveal, unblock, uncase, unclog, unclutch, uncork, uncover, uncurtain, undo, undrape, unfold, unfoul, unlatch, unlock, unplug, unroll, unseal, unsheathe, unshut, unstop, unveil, unwrap

Etymology
From un- + clench.