European opening competition (5)
I believe the answer is:
event
'competition' is the definition.
(I've seen this before)
'european opening' is the wordplay.
'european' becomes 'e' (abbreviation e.g. EU).
'opening' becomes 'vent' (vent is a kind of opening).
'e'+'vent'='EVENT'
(Other definitions for event that I've seen before include "important" , "Planned public or social occasion" , "riding competition" , "Episode" , "Thing that happens" .)