Alternative to a convertible (5)
I believe the answer is:
sedan
'alternative to a convertible' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for sedan that I've seen before include "big chair" , "Enclosed chair" , "Dean's in an old conveyance" , "Andes (anag.)" , "Covered chair carried between poles" .)