Take the battery out.
Also accept the risk that the gift wrapping will be opened so pack more gift wrapping paper.
I would also not lock the bag or accept that the lock will be broken to facilitate a manual check of the bag.

No problem checking in a wall clock in the bag. Just allow any security check to easily see that it is just a clock.

I find my checked luggage going through a manual security check (i.e. opened) when I put a litre bottle of mineral water (unopened) in there.

How you feel if another passenger checked in a working clock and security did not check up on it. How would anyone know, apart from yourself, that it was not just a harmless clock.