A foreign sensation, but hard-hearted (9)
I believe the answer is:
unfeeling
'hard-hearted' is the definition.
(I've seen this before)
'a foreign sensation' is the wordplay.
'a foreign' becomes 'un' ('a' translated into French).
'sensation' becomes 'feeling' (I've seen this before).
'un'+'feeling'='UNFEELING'
'but' acts as a link.
(Other definitions for unfeeling that I've seen before include "Heartless" , "Callous" , "Hard-hearted" , "Lacking in sympathy or emotion" .)