Notwithstanding this, expectorate into British river (7)
I believe the answer is:
despite
'notwithstanding' is the definition.
(notwithstanding means despite or nevertheless)
'expectorate into british river' is the wordplay.
'expectorate' becomes 'spit' (spitting is a kind of expectorating).
'into' indicates putting letters inside.
'british river' becomes 'dee' (River Dee. I am not sure about the 'british' bit.).
'spit' inserted into 'dee' is 'DESPITE'.
'this' is the link.
Can you help me to learn more?
(Other definitions for despite that I've seen before include "Undeterred" , "Without being affected by; contempt" , "In the face" , "Notwithstanding" , "Regardless of, in defiance of" .)