Car frequently breaks down (4,3)
I believe the answer is:
soft top
'car' is the definition.
(I've seen this before)
'frequently breaks down' is the wordplay.
'frequently' becomes 'oft' (oft can mean frequently, eg oft-quoted).
'breaks' indicates putting letters inside (inserted letters break into the word).
'down' becomes 'stop' (I am not sure about this - if you are sure you should believe this answer much more).
'oft' inserted within 'stop' is 'SOFT-TOP'.
Can you help me to learn more?
(Other definitions for soft top that I've seen before include "Alternative to saloon" , "Fancy car" , "Car with a folding roof" , "Type of convertible car" , "Vehicle" .)