Tough puzzle – a stunner inspiring ecstasy (6)
I believe the answer is:
teaser
'tough puzzle' is the definition.
'teaser' can be an answer for 'puzzle' (I've seen this before). I'm not sure about the 'tough' bit.
'a stunner inspiring ecstasy' is the wordplay.
'a stunner' becomes 'taser' (weapon which stuns or shocks).
'inspiring' indicates putting letters inside.
'ecstasy' becomes 'E' (informal term for the drug).
'taser' enclosing 'e' is 'TEASER'.
Can you help me to learn more?
(Other definitions for teaser that I've seen before include "Puzzling question or gentle goader" , "A difficult problem of Teresa" , "Conundrum" , "One who annoys people or cards wool" , "Difficult question" .)