Speed in car at Essen (4)
I believe the answer is:
rate
'speed' is the definition.
(both can mean pace)
'in car at essen' is the wordplay.
'in' says the answer is hidden in the clue.
'RATE' is hidden within 'car at essen'.
(Other definitions for rate that I've seen before include "Amount measured against another" , "Rank; fee" , "Bawl out" , "Be worthy of; speed" , "Assess or grade" .)