Argues ecstasy is in short supply (6)
I believe the answer is:
sparse
'in short supply' is the definition.
(sparse can mean meagre or minimal)
'argues ecstasy' is the wordplay.
'argues' becomes 'spars' (sparring is a kind of arguing).
'ecstasy' becomes 'E' (informal term for the drug).
'spars'+'e'='SPARSE'
'is' is the link.
(Other definitions for sparse that I've seen before include "Infrequent" , "rarely occurring" , "Thinly dotted about" , "Thinly dispersed" , "Far from lavish" .)