phrasal-verb
clam up with
恥ずかしさや恐怖で突然話すのをやめる
Meaning
to suddenly stop talking because of shyness or fear
Example
He **clammed up with** embarrassment when everyone stared at him.
彼は恥ずかしさで黙り込んだ、みんなが彼を見つめたとき。