Italian greeting found in Chicago every now and again (4)
I believe the answer is:
ciao
'italian greeting' is the definition.
(I've seen this in another clue)
'chicago every now and again' is the wordplay.
'every now and again' indicates alternate letters.
The alternate letters of 'chicago' are 'CIAO'.
'found in' is the link.
(Other definitions for ciao that I've seen before include "Italian cheerio" , "Italian hello-goodbye" , "farewell" , "Italian salutation" , "See you in Italy" .)