Ecstasy's the reason for showing a lot of feeling (7)
I believe the answer is:
emotive
'showing a lot of feeling' is the definition.
(I've seen this in another clue)
'ecstasy's the reason' is the wordplay.
'ecstasy' becomes 'E' (informal term for the drug).
'the reason' becomes 'motive' (I've seen this in another clue).
'e'+'motive'='EMOTIVE'
'for' acts as a link.
(Other definitions for emotive that I've seen before include "ignoring rationality?" , "Argumentative" , "Stimulating to feelings" , "Deeply felt" , "Highly-charged" .)