Bedeutung von “clam up” — Learner’s Dictionary

clam up

informal phrasal verb with clam us uk /klæm/ verb present participle clamming, past tense and past participle clammed

to suddenly stop talking, usually because you are embarrassed or nervous:

He was afraid he would clam up in front of the television camera.

(Definition von “clam up” aus dem Cambridge Learner's Dictionary © Cambridge University Press)