High vault full of metal (6)
I believe the answer is:
stinky
'high' is the definition.
(I've seen this before)
'vault full of metal' is the wordplay.
'vault' becomes 'sky' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'full of' indicates putting letters inside.
'metal' becomes 'tin' (tin is a kind of metal).
'sky' going around 'tin' is 'STINKY'.
Can you help me to learn more?
(Other definitions for stinky that I've seen before include "Foul-smelling" , "high" , "Having an unpleasant smell" , "Humming" , "Odoriferous" .)