Taciturn, reserved (8)
I believe the answer is:
reticent
I believe this clue is a double definition.
'taciturn' is the first definition.
(similar in meaning)
'reserved' is the second definition.
(synonyms)
(Other definitions for reticent that I've seen before include "Secretive" , "Reserved, retiring" , "Uncommunicative" , "Not wanting to talk" , "Reserved, loath to talk" .)