Magnate at last opening show (5)
I believe the answer is:
event
'show' is the definition.
The definition and answer can be both acts as well as being singular nouns.
Maybe you can see a link between them that I can't see?
'magnate at last opening' is the wordplay.
'at last' suggests the final letters.
'opening' becomes 'vent' (vent is a kind of opening).
The final letter of 'magnate' is 'e'.
'e'+'vent'='EVENT'
Can you help me to learn more?
(Other definitions for event that I've seen before include "High jump, say" , "horse-riding competition" , "Thing that happens" , "celebration?" , "400 metres?" .)