Silenced taciturn detective (5)
I believe the answer is:
muted
'silenced' is the definition.
(muting is a kind of silencing)
I don't understand the rest of the clue.
Can you help me to learn more?
(Other definitions for muted that I've seen before include "with reduced volume" , "Hushed or stifled" , "Of great weight" , "Kept quiet" , "Dull" .)