Hallucinogen produced from stale dung (5,4)
I believe the answer is:
Here is my best explanation:
'hallucinogen' is the definition.
(angel dust is a kind of hallucinogen)
'from stale dung' is the subsidiary indication.
'from' indicates an anagram (from the letters).
'staledung' anagrammed gives 'angeldust'.
'produced' is the link.
(Another definition for angel dust that I've seen is "Hallucinogen - stale dung (anag)".)