How drivers could see they were behind a dogcart? (4,5)
I believe the answer is:
tail light
'how drivers could see they' is the definition.
I know nothing about this answer so I can't judge whether it can be defined by this definition.
'behind a dogcart?' is the wordplay.
'behind' becomes 'tail' (synonyms).
'a dogcart?' becomes 'light' (I can't explain this - if you can you should believe this answer much more).
'tail'+'light'='TAIL-LIGHT'
'were' is the link.
Can you help me to learn more?
(Other definitions for tail light that I've seen before include "car shows it braking" , "followers'll see it" , "rear lamp" , "motoring requisite" , "Feature of Rover, say" .)