Wonderful feeling of insouciance reduced by then dropping ecstasy (5)
I believe the answer is:
bliss
'ecstasy' is the definition.
(I've seen this before)
I cannot understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for bliss that I've seen before include "of composing?" , "promise of afterlife" , "One who scored" , "Seventh 13 across" , "Sheer delight" .)