Habitually silent (8)
I believe the answer is:
taciturn
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">habitually silent</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for taciturn that I've seen before include "Reserved, saying little" , "withdrawn" , "Disinclined towards conversation" , "Habitually uncommunicative, saying little" , "Habitually silent" .)