Medical emergency vehicle to help overturned motor with support (7,6)

'medical emergency' is the definition.
(a cardiac arrest is a medical emergency)

'vehicle to help overturned motor with support' is the wordplay.
I cannot really understand how this works, but
'vehicle' could be 'car' (car is a kind of vehicle) and 'car' is found in the answer.
'motor' could be 'car' (informal term for car) and 'car' is found in the answer.
'support' could be 'rest' (e.g. a shoulder rest is a support for shoulder) and 'rest' is present in the answer.
The remaining letters 'dia' is a valid word which might be clued in a way I don't understand.
This may be the basis of the clue (or it may be nonsense).