One providing the final act with thank-you party taking place in less than a full month (7)
I believe the answer is:
matador
'one providing the final act' is the definition.
The answer is a person as well as being a singular noun. This is suggested by the definition.
'thank-you party taking place in less than a full month' is the wordplay.
I cannot quite understand how this works, but
'party' could be 'do' (do can informally mean a party) and 'do' is present in the answer.
'a' is found in the answer.
'month' could be 'm' (standard abbreviation) and 'm' is present in the answer.
'thank you' could be 'ta' (informal way of saying thank you) and 'ta' is found within the answer.
A single letter 'r' remains which might be clued in a way I don't see.
This may be the basis of the clue (or it may be nonsense).
'with' acts as a link.
Can you help me to learn more?
(Other definitions for matador that I've seen before include "he aims to get a bull" , "Ring butcher" , "Spaniard that fights" , "who does for bulls" , "A bull-fighter.11 Beginning to develop" .)