clam up

v.

拒不开口；三缄其口；

Clam Up
Clam up!
Financial Firms Clam Up
Brooklyn: Come hungry, clam up
Don’t clam up on National Threatened Species Day
Philippa Gee: Why do funds clam up when performance sours?
Despite contractual obligations to clam up, some folks can't can the chatter
Culture Behind "Clam Up Behavior"among Donors Who Received Living Liver-Transplantation at a Hospital in Japan
Employment Lawyers Rethink Advice: Employers need not clam up when asked for job references, some say
Malchiodi, C. A., & Crenshaw, D. A. (Eds.). (2017). What to Do When Children Clam Up in Psychotherapy: Interventions to Facilitate C...