Cash box is guarded (4)
I believe the answer is:
safe
This could be a double definition.
'cash box' is the first definition.
'safe' can be an answer for 'box' (safe is a kind of box). I'm not certain of the 'cash' bit.
'is guarded' is the second definition.
(I've seen this in another clue)
Can you help me to learn more?
(Other definitions for safe that I've seen before include "Protected from danger" , "Metal box for security" , "Harmless" , "Uninjured; excellent; lockable cabinet" , "Uninjured, secure" .)