guarded
adjective
uk/ˈɡɑːdɪd/ uscareful not to give too much information or show how you really feel:
a guarded response
Conversation on the trading floor tends to be polite but guarded.
protected from being known, found, harmed, or taken:
carefully/closely/fiercely guarded a carefully guarded secret
guardedly
adverb
We are guardedly optimistic about the economy.