Explosive device in birdcage, say? (5,4)

I believe the answer is:

booby trap

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This clue could be a double definition.

'explosive' is the first definition.
(I know that booby trap is a type of mine)

'device in birdcage say?' is the second definition.
'booby trap' can be an answer for 'device' (booby trap is a kind of device). I'm not certain of the 'in birdcage say?' bit.

Can you help me to learn more?

(Other definitions for booby trap that I've seen before include "hidden hazard" , "mine?" , "concealed danger" , "Unexpected explosive device" , "Lethal or playful device set off by victim" .)

I've seen this clue in The Guardian.

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