Long story involving European (5)
I believe the answer is:
yearn
'long' is the definition.
('yearn' can be a synonym of 'long')
'story involving european' is the wordplay.
'story' becomes 'yarn' ('yarn' can be a synonym of 'story').
'involving' means one lot of letters goes inside another.
'european' becomes 'e' (abbreviation e.g. EU).
'yarn' enclosing 'e' is 'YEARN'.
(Other definitions for yearn that I've seen before include "Hanker" , "wish" , "Have a great longing" , "Have strong desire" , "Long (for something)" .)