Dawn insures convertible (7)
I believe the answer is:
sunrise
'dawn' is the definition.
('sunrise' can be a synonym of 'dawn')
'insures convertible' is the wordplay.
'convertible' indicates anagramming the letters.
'insures' anagrammed gives 'SUNRISE'.
(Other definitions for sunrise that I've seen before include "It's preceded by dawn" , "What follows dawn" , "The first light of day" , "Tequila --, cocktail" , "Type of industry" .)