Affirmations of my fine morals are vacuous at last (5)
I believe the answer is:
yeses
'affirmations' is the definition.
(I know that yes is a type of affirmations)
'my fine morals are vacuous at last' is the wordplay.
'at last' says to take the final letters.
The last letters of 'my fine morals are vacuous' are 'YESES'.
'of' is the link.
(Other definitions for yeses that I've seen before include "Consenting answers" , "Positive answers" , "agreements" , "Votes in favour" .)