Dig swinging German coming up on ecstasy (4)
I believe the answer is:
gibe
'dig' is the definition.
(I know that dig can be written as gibe)
'swinging german coming up on ecstasy' is the wordplay.
'swinging' becomes 'bi' (I've seen this in other clues).
'german' becomes 'g' (abbreviation).
'coming up' shows that the letters should be reversed in order (in a down clue, letters go up).
'on' means one lot of letters go next to another.
'ecstasy' becomes 'E' (informal term for the drug).
'bi'+'g'='big'
'big' back-to-front is 'gib'.
'gib'+'e'='GIBE'
(Other definitions for gibe that I've seen before include "Mocking remark" , "Barb, dig" , "Dig, or a barbed comment" , "Jeer, mock" , "Hurtful remark" .)