Dooglus, thank You.
One more question, unlocking for staking is valid for some time or until wallet is closed?
I am considering to put 5 btc on staking (in Clam of course) for long time.
Safety is very important for me.
Am I safe if wallet.dat is stolen and encrypted (but unlocked for staking only).
I can't answer for sure but I'd say the decryption happens in memory only, not "on disk", so your wallet.dat file will still be encrypted.
But there are two other security concerns I can think of, which apply if the attacker has control over your computer (rather than something less sophisticated like stealing your wallet.dat via an accidental network share)
1. A key logger. This will give the attacker your password as you type it.
2. If the attacker can read arbitrary memory locations, they may be able to locate the decrypted private keys that are necessary to stake.
If you're going to invest 5 BTC it may be worth considering building a custom machine. Lock it down tight, and only allow outbound connects on the CLAM port. Disallow everything else.