phrasal verbphr vinformalTALK TO somebody to suddenly stop talking, especially when you are nervous or shy 〔尤指因紧张、害羞而〕突然闭口,突然沉默不语
A sensitive child is likely just to clam up.
敏感的孩子可能就会闭口不言。
Examples from the Corpus
clam up• He always clams up when I ask him about his job -- do you think he's doing something illegal?• The police took her in for questioning, but she clammed up when they asked about her boyfriend.