Bird, mine, in aircraft compartment (7)
I believe the answer is:
cockpit
'aircraft compartment' is the definition.
'cockpit' can be an answer for 'compartment' (cockpit is a kind of compartment). I'm not sure about the 'aircraft' bit.
'bird mine' is the wordplay.
'bird' becomes 'cock' (cock is a kind of bird).
'mine' becomes 'pit' (down the pit).
'cock'+'pit'='COCKPIT'
'in' acts as a link.
Can you help me to learn more?
(Other definitions for cockpit that I've seen before include "Pilot's cabin" , "In a plane, the pilot sits in this space" , "Pilot's place in aircraft" , "battlefield" , "not suitable for a hen party" .)