A hand with the fingers clenched in the palm (as for hitting)(noun)
WordNet. Princeton University. 2010.
Use "clenched fist" in a sentence
""Bwana Sinclair," announced this venerable gentleman, holding up a clenched fist for silence."
"The clenched fist hit the ta-bletop and made the dishes dance."
"Of course, the intervention of RCD Battle Group was of fundamental importance since it alone possessed the power of a closely clenched fist hitting the enemy in a soft spot."