Ecstasy left me in hospital department getting oxygen, say? (7)
I believe the answer is:
element
'oxygen say?' is the definition.
(oxygen is a kind of element)
'ecstasy left me in hospital department' is the wordplay.
'ecstasy' becomes 'e' (informal term for the drug).
'left' becomes 'l' (common abbreviation**).
'in' means one lot of letters goes inside another.
'hospital department' becomes 'ent'.
'me' placed inside 'ent' is 'ement'.
'e'+'l'+'ement'='ELEMENT'
'getting' acts as a link.
(Other definitions for element that I've seen before include "Constituent of universe" , "Basic chemical unit" , "Basic constituent; aspect" , "Singular ingredient" , "Primary chemical substance" .)