Sounding the horn in an area of London (7)
I believe the answer is:
tooting
'sounding' is the definition.
(tooting is a kind of sounding)
'the horn in an area of london' is the wordplay.
I cannot really understand how this works, but
'the' could be 't' (the is pronounced as a 't' sound in some dialects) and 't' is found within the answer.
'in' is found in the answer.
'of' could be 'o' and 'o' is present in the answer.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for tooting that I've seen before include "Showing impatience as driver" , "S. London district" , "Evidence of impatient motorist" , "South London area" , "Blasting a horn" .)