I'm in Los Angeles, an American city (4)
I believe the answer is:
lima
'an american city' is the definition.
'lima' can be an answer for 'city' (Lima is an example). I am not certain of the 'an american' bit.
'i'm in los angeles' is the wordplay.
'i'm' becomes 'im' ().
'in' is an insertion indicator.
'los angeles' becomes 'LA' (abbreviation).
'im' put within 'la' is 'LIMA'.
Can you help me to learn more?
(Other definitions for lima that I've seen before include "distant city" , "Mail to Peru'd capital" , "Kind of bean" , "Edible bean; capital city" , "Mail it to Peruvian city" .)