Los Angeles has three quarters with narrow streets (5)
I believe the answer is:
lanes
'narrow streets' is the definition.
(I've seen this in another clue)
'los angeles has three quarters' is the wordplay.
'three quarters' can mean three replacements for 'quarter'.
'los angeles' becomes 'LA' (abbreviation).
'has' says to put letters next to each other.
'quarter' becomes 'n' ().
'quarter' becomes 'e'.
'quarter' becomes 's'.
'la'+'n'+'e'+'s'='LANES'
'with' acts as a link.
(Other definitions for lanes that I've seen before include "Narrow roads or road divisions" , "Narrow tracks or paths" , "Tracks for traffic" , "Leans into narrow roads" , "Country roads" .)