And garden he dug up to find an explosive device (4,7)
I believe the answer is:
hand grenade
This might be a double definition.
'and garden he dug up' is the first definition.
Although both the answer and definition are singular nouns, I can't see how they can define each other.
'an explosive device' is the second definition.
(hand grenade is a kind of explosive device)
'to find' acts as a link.
Can you help me to learn more?
(Other definitions for hand grenade that I've seen before include "pineapple" , "Small explosive device for throwing" , "Explosive device that is thrown" , "Small thrown bomb" , "Military explosive" .)