Rest in quiet with excellent port (8)
I believe the answer is:
shanghai
'port' is the definition.
(I've seen this before)
'rest in quiet with excellent' is the wordplay.
'rest' becomes 'hang' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'in' means one lot of letters goes inside another.
'quiet' becomes 'sh' (both can be said to tell someone to be quiet).
'with' is a charade indicator (letters next to each other).
'excellent' becomes 'ai' (resembles 'Ah', old-fashioned term for excellent).
'hang' going within 'sh' is 'shangh'.
'shangh'+'ai'='SHANGHAI'
Can you help me to learn more?
(Other definitions for shanghai that I've seen before include "Might the Shah gain in China?" , "Kidnap sailors" , "Press-gang" , "It's wrong to gain hash in the Chinese city" , "Port city on the Yangtze estuary" .)