Storage space allows length of cloth to fit in vehicle (6)
I believe the answer is:
cellar
'storage space' is the definition.
(cellar is a kind of storage space)
'length of cloth to fit in vehicle' is the wordplay.
'length of cloth' becomes 'ell' (historical fabric measurement).
'to fit in' is an insertion indicator.
'vehicle' becomes 'car' (car is a kind of vehicle).
'ell' put within 'car' is 'CELLAR'.
'allows' acts as a link.
(Other definitions for cellar that I've seen before include "wine stocks" , "Where provisions may be stored" , "Wine vault" , "Container for salt" , "Room where wine is stored (6)," .)