Noncommittal (5)
(Other definitions for vague that I've seen before include "Indistinct or not clearly expressed" , "Indistinct or imprecise" , "Not clearly expressed, woolly" , "Imprecise (in thought)" , "not focused" .)
'noncommittal' is the definition.
(synonyms)
This is the entire clue.
(Other definitions for guarded that I've seen before include "Cautious, having reservations" , "Cautious; watched over" , "with escort" , "Very reluctant to give out information" , "Wary" .)