Providing a coat, king leaves, departing (9)
I believe the answer is:
vanishing
'providing' is the definition.
The definition and answer can be both acts as well as being singular nouns.
Maybe they are linked in a way I don't understand?
'a coat king leaves departing' is the wordplay.
I cannot really see how this works, but
'a' could be 'an' and 'an' is found in the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Another definition for vanishing that I've seen is " Disappearing".)