She clenched up her teeth to stop herself from screaming.
fists
Frequency:
55
%
She clenched up her fists in determination.
jaw
Frequency:
50
%
He clenched up his jaw to control his emotions.
muscles
Frequency:
45
%
The athlete clenched up his muscles before the race.
Idiomatic Expressions for clench up
Phrase: make someone clench up
Meaning: to cause someone to tighten their muscles out of stress, fear, or anger
Usage: The loud noise made him clench up in fear.