Unforthcoming (3)
(Other definitions for taciturn that I've seen before include "Reticent" , "Aloof" , "Reserved, saying little" , "Uncommunicative, of few words" , "Talking little" .)
'unforthcoming' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for reserved that I've seen before include "Retiring" , "without emotion" , "Spoken for" , "Set aside; reticent" , "Bashful" .)
'unforthcoming' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for coy that I've seen before include "Military team in brief" , "reluctant to divulge information" , "not forthcoming" , "Pretending to be shy or bashful" , "Group of soldiers" .)