Vehicle staying outside reduced opening in garage (7)
I believe the answer is:
carport
'garage' is the definition.
(carport is a kind of garage)
'vehicle staying outside reduced opening in' is the wordplay.
'vehicle' becomes 'car' (car is a kind of vehicle).
'staying outside' becomes 'pot' (I can't explain this - if you can you should believe this answer much more).
'opening' says to take the initial letters.
'in' indicates putting letters inside.
The first letter of 'reduced' is 'r'.
'pot' going around 'r' is 'port'.
'car'+'port'='CARPORT'
(Other definitions for carport that I've seen before include "makeshift garage" , "off-road parking" , "vehicle cover" , "Vehicle shelter" , "Space in lieu of garage" .)