North African vessel sits in Arno now and then (8)
I believe the answer is:
tunisian
'north african' is the definition.
(I've seen this before)
'vessel sits in arno now and then' is the wordplay.
'vessel' becomes 'tun' (type of vessel for beer).
'sits' becomes 'is' (I can't justify this - if you can you should give a lot more credence to this answer).
'now and then' means one should take alternating letters (letters taken on a regular basis, now and then).
'in'+'arno'='inarno'
The alternating letters of 'inarno' are 'ian'.
'tun'+'is'+'ian'='TUNISIAN'
Can you help me to learn more?
(Another definition for tunisian that I've seen is " North African native".)