US city worker into almost all maps (7)
I believe the answer is:
atlanta
'us city' is the definition.
(I've seen this before)
'worker into almost all maps' is the wordplay.
'worker' becomes 'ant' (worker is a type of ant).
'into' means one lot of letters goes inside another.
'almost all' means to remove the last letter.
'maps' becomes 'atlas' (printed collection of maps).
'atlas' with its last letter taken off is 'atla'.
'ant' put inside 'atla' is 'ATLANTA'.
(Other definitions for atlanta that I've seen before include "Georgian location" , "American city" , "City plundered and burned by Sherman's army, 1864" , "southern US city" , "Site of 1996 Olympics" .)