In storm, commercial vehicle is waterproof (9)
I believe the answer is:
galvanise
'waterproof' is the definition.
Both the definition and answer are verbs in their base form.
Maybe you can see a link between them that I can't see?
'in storm commercial vehicle is' is the wordplay.
'in' indicates putting letters inside.
'storm' becomes 'gale' (a gale is a windy storm).
'commercial vehicle' becomes 'van' (I've seen this before).
'van'+'is'='vanis'
'gale' placed around 'vanis' is 'GALVANISE'.
Can you help me to learn more?
(Other definitions for galvanise that I've seen before include "Electrify" , "subject to action of electric current" , "Excite" .)