Spaniard's "house white" is port (10)
I believe the answer is:
casablanca
'is port' is the definition.
(I have seen 'Moroccan port' mean 'casablanca' so perhaps 'port' could also mean 'casablanca')
'spaniard's house white' is the wordplay.
I cannot quite see how this works, but
'house' could be 'casa' (Spanish word for 'house' also used in English) and 'casa' is located in the answer.
'white' could be 'blanc' (I've seen this before) and 'blanc' is found in the answer.
A single letter 'a' remains which might be clued in a way I don't understand.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for casablanca that I've seen before include "Famous Bogart film" , "romantic movie" , "Bogart movie" , "City and port of Morocco" , "Foreign counterpart of White House" .)