Having no Ecstasy, supply crack (4)
I believe the answer is:
quip
'crack' is the definition.
(I've seen this before)
I don't understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for quip that I've seen before include "Clever comment" , "Wisecrack" , "Verbal sally" , "Quick witty remark" , "clever observations" .)