At the very end enters to administer minuscule amount (8)
I believe the answer is:
terminus
'amount' is the definition.
(terminus is a kind of amount)
'at the very end enters to administer minuscule' is the wordplay.
'TERMINUS' is hidden within the letters.
But, I am unsure how this is indicated.
Can you help me to learn more?
(Other definitions for terminus that I've seen before include "Last stop" , "boundary marker" , "End, extremity" , "Final station on bus route" , "Limit" .)