Thumbs up, Badenoch predominantly struck dumb (5)
I believe the answer is:
shtum
'dumb' is the definition.
(I've seen this before)
I can't explain the remainder of the clue.
Can you help me to learn more?
(Other definitions for shtum that I've seen before include "silence" , "Quiet" , "Silent, dumb (sl.)" , "Silent, non-communicative" , "tight-lipped" .)