Now and then, pair stay in city of 1 (4)
I believe the answer is:
pisa
'city of 1' is the definition.
'pisa' can be an answer for 'city' (Pisa is an example). I'm not certain of the 'of 1' bit.
'now and then pair stay' is the wordplay.
'now and then' indicates alternate letters (letters taken on a regular basis, now and then).
'pair'+'stay'='pairstay'
The alternate letters of 'pairstay' are 'PISA'.
'in' is the link.
Can you help me to learn more?
(Other definitions for pisa that I've seen before include "Italian city with leaning tower" , "City with listed building" , "Place with leaning tower" , "listed building site" , "Location of leaning tower" .)