Portuguese capital (6)
![Ross](/clue/static/ross-mug.min.png)
I believe the answer is:
lisbon
'portuguese capital' is the definition.
(capital of Portugal)
This is all the clue.
(Other definitions for lisbon that I've seen before include "Capital of Portugal" , "Slob in Portuguese city" , "Capital city on the Tagus" , "Portugal's capital" , "European capital" .)