European sensing English rather bitter, first of all (4)
I believe the answer is:
serb
'european' is the definition.
(person from Serbia)
'sensing english rather bitter first of all' is the wordplay.
'first of all' says to take the initial letters.
The first letters of 'sensing english rather bitter' is 'SERB'.
(Other definitions for serb that I've seen before include "One from Belgrade" , "Balkan native" , "From Belgrade, perhaps" , "Eastern European" , "A European national" .)