End of the opening contest (5)
I believe the answer is:
event
'contest' is the definition.
(thesaurus)
'end of the opening' is the wordplay.
'end of' says to take the final letters.
'opening' becomes 'vent' (vent is a kind of opening).
The final letter of 'the' is 'e'.
'e'+'vent'='EVENT'
(Other definitions for event that I've seen before include "Occurence, happening" , "Something that takes place" , "tournament" , "A thing taking place" , "Occurence, occasion" .)