US city overturns farmyard noise permits (6)

I believe the answer is:

allows

I'm a little stuck... Click here to teach me more about this clue!

'permits' is the definition.
(I know this)

'us city overturns farmyard noise' is the wordplay.
'us city' becomes 'la' (Los Angeles).
'overturns' says the letters should be written in reverse.
'farmyard noise' becomes 'lows' (I can't justify this - if you can you should believe this answer much more).
'la' back-to-front is 'al'.
'al'+'lows'='ALLOWS'

Can you help me to learn more?

(Other definitions for allows that I've seen before include "Permits or agrees" , "Grants leave" , "Sallow (anag.)" , "Permits, lets" , "Tolerates" .)

I've seen this clue in the Sydney Morning Herald.

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