Ecstasy seen in something magical is diminished (5)
I believe the answer is:
waned
'diminished' is the definition.
(waning is a kind of diminishing)
I don't understand the remainder of the clue.
Can you help me to learn more?
(Other definitions for waned that I've seen before include "Decreased in size" , "grew faint" , "Ebbed; declined" , "(Of moon) grew smaller" .)