European cause becoming controversial (7)
I believe the answer is:
emotive
'controversial' is the definition.
(I've seen this before)
'european cause' is the wordplay.
'european' becomes 'E' (abbreviation e.g. EU).
'cause' becomes 'motive'.
'e'+'motive'='EMOTIVE'
'becoming' acts as a link.
(Other definitions for emotive that I've seen before include "Eliciting intense feeling" , "Stirring feeling" , "Stimulating to feelings" , "Affecting, moving" , "arousing passion" .)