Hold up Ecstasy to be swallowed by crazy lady (5)
I believe the answer is:
delay
'hold up' is the definition.
(I know that hold up can be written as delay)
'ecstasy to be swallowed by crazy lady' is the wordplay.
'ecstasy' becomes 'E' (informal term for the drug).
'to be swallowed by' means one lot of letters goes inside another.
'crazy' is an anagram indicator.
'lady' anagrammed gives 'dlay'.
'e' put within 'dlay' is 'DELAY'.
(Other definitions for delay that I've seen before include "Hinder" , "Hold-up, time lag" , "Hold back" , "Postponement" , "hold-up of train?" .)