Munitions finally kept in alpine garden (8)
I believe the answer is:
rocketry
'munitions' is the definition.
Although both the answer and definition are singular nouns, I don't understand how one could define the other.
'finally kept in alpine garden' is the wordplay.
I cannot really see how this works, but
'garden' could be 'rock' (rock garden is a kind of garden) and 'rock' is present in the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for rocketry that I've seen before include "Branch specialised in launching" , "Complex science" , "Propulsion of missiles" , "Clever science" , "NASA's expertise" .)