A herb doctor produced a course of treatment (5)
I believe the answer is:
rehab
'treatment' is the definition.
(I have seen 'remedial treatment' mean 'rehab' so perhaps 'treatment' could also mean 'rehab')
'a herb doctor' is the wordplay.
'doctor' indicates anagramming the letters.
'a'+'herb'='aherb'
'aherb' with letters rearranged gives 'REHAB'.
'produced a course of' acts as a link.
This may not be right. Some or all of it may be part of another bit of the clue.
(Other definitions for rehab that I've seen before include "remedial treatment" , "Process of restoring, eg, an addict to health" , "Treatment for dependency" , "Rehabilitation (abbrev.)" , "help with addiction" .)