clamming up

After his parents’ rough divorce, why is this 4-year-old clamming up?

By clamming up, they empower Trump to curb-stomp more and more of our democratic values, while they quiver in the corner afraid of Trump deploying his Red Hats against them in another late-night tweetstorm.

Investigators said those who were clamming up included the bride, KPRC-TV reported.

After his parents’ rough divorce, why is this chatty 4-year-old clamming up?

You’re certainly responding in a textbook way: doubting yourself, clamming up, taking his word as gospel.