Uncommunicative (8)
There are a few possibilities for this:
withdrawn
'uncommunicative' is the definition.
(associated in meaning)
This is the entire clue.
(Other definitions for taciturn that I've seen before include "Talking little" , "Aloof" , "Far from talkative" , "withdrawn" , "Disinclined towards conversation" .)
(Other definitions for retiring that I've seen before include "Shy, avoiding company" , "Quiet" , "Like an unassertive person" , "stepping back" , "Timid" .)
'uncommunicative' is the definition.
(thesaurus)
This is the entire clue.
(Other definitions for withdrawn that I've seen before include "Rather shy" , "Quiet" , "Shy, reserved" , "Pulled out of" , "Discontinued; shunning social contact" .)