Doctor in proctologist's area of expertise has little time for hallucinogen (5,4)

'hallucinogen' is the definition.
(angel dust is a kind of hallucinogen)

'doctor in proctologist's area of expertise has little time' is the wordplay.
I cannot quite understand how this works, but
'doctor' could be 'geld' (both can mean to neuter an animal) and 'geld' is found in the answer.
'area' could be 'a' (maths abbreviation) and 'a' is present in the answer.
'time' could be 't' and 't' is found within the answer.
This may be the basis of clue (or it may be nonsense).

'for' is the link.