Is it instrumental in warning Parisian pedestrians? (6,4)
I believe the answer is:
french horn
'instrumental in warning parisian pedestrians?' is the definition.
Although both the answer and definition are singular nouns, I can't understand how one could define the other.
I don't understand the remainder of the clue.
Can you help me to learn more?
(Other definitions for french horn that I've seen before include "Brass musical instrument" , "Wind instrument" , "part of a broken-down 27 [CARTHORSE]?" .)