City company without atmosphere (5)
I believe the answer is:
cairo
'city' is the definition.
(Cairo is an example)
'company without atmosphere' is the wordplay.
'company' becomes 'co' (abbreviation).
'without' means one lot of letters goes inside another ('without' can be similar in meaning to 'outside').
'atmosphere' becomes 'air' (synonyms).
'co' going around 'air' is 'CAIRO'.
(Other definitions for cairo that I've seen before include "Port upstream from the Nile delta" , "Capital of Egypt" , "Egyptian capital" , "Capital city on the Nile" , "Al Qahira" .)