Sounds like the inevitable event for charity (4)
I believe the answer is:
fete
'charity' is the definition.
The definition and answer can be both acts as well as being singular nouns.
Maybe there's an association between them I don't understand?
I don't understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for fete that I've seen before include "Organised outdoor party or charitable event" , "Fundraising event" , "Outdoor entertainment and sale, often for charity" , "Festival event" , "Village festival" .)