Ecstasy, see, when one’s out for a duck (5)
I believe the answer is:
evade
'a duck' is the definition.
(I've seen this before)
'ecstasy see when one's out' is the wordplay.
I cannot really understand how this works, but
'ecstasy' could be 'e' (informal term for the drug) and 'e' is found in the answer.
'see' could be 'v' (Latin 'vide', used to direct a reader to a source) and 'v' is found in the answer.
'when' could be 'e' (I've seen this in other clues) and 'e' is found within the answer.
'one' could be 'a' and 'a' is located in the answer.
A single letter 'd' remains which might be clued in a way I don't see.
This may be the basis of clue (or it may be nonsense).
'for' is the link.
(Other definitions for evade that I've seen before include "To get away from" , "avoid answering" , "Dodge or equivocate" , "Circumvent, dodge" , "Shun, escape" .)