In poor health - result of a car accident? (3,4)
I believe the answer is:
run down
'in poor health' is the definition.
(I've seen this before)
I can't explain the rest of the clue.
Can you help me to learn more?
(Other definitions for run down that I've seen before include "Tired - shabby - criticise" , "brief review" , "slate" , "not very well" , "pan?" .)