Perhaps the bra is mine? (5,4)
I believe the answer is:
booby trap
'mine?' is the definition.
(booby trap is a kind of mine)
I cannot understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for booby trap that I've seen before include "hidden bomb, perhaps" , "concealed danger" , "mine?" , "Unexpected explosive device" , "Device for practical joke" .)