Bird had to protect its home in national property (5,6)

'national property' is the definition.
I don't know anything about this answer so I cannot judge whether this works.

'bird had to protect its home' is the wordplay.
I cannot quite see how this works, but
'bird' could be 'crow' (crow is a kind of bird) and 'crow' is located in the answer.
'had' could be 'ate' ('have' can mean 'eat') and 'ate' is present in the answer.
'home' could be 'nest' (a bird's home) and 'nest' is located in the answer.
No letters remain.
This may be the basis of the clue (or it may be nonsense).

'in' acts as a link.

Can you help me to learn more?