Guarded, wary (8)
I believe the answer is:
cautious
This clue is a double definition.
'guarded' is the first definition.
(similar in meaning)
'wary' is the second definition.
(similar in meaning)
(Other definitions for cautious that I've seen before include "Careful to avoid dangers" , "Prudent, slow to take a chance" , "safe" , "Unadventurous" , "Tentative" .)