Port's name engraved in seat (6)
I believe the answer is:
nantes
'port's' is the definition.
(I've seen this before)
'name engraved in seat' is the wordplay.
'name' becomes 'Nan'.
'engraved in seat' becomes 'tes' (I can't justify this - if you can you should give a lot more credence to this answer).
'nan'+'tes'='NANTES'
Can you help me to learn more?
(Other definitions for nantes that I've seen before include "port abroad" , "Site of historic drownings" , "Western French port" , "City and port of W. France on the Loire" , "French Atlantic port" .)