Teacher’s disorder cured at hydro, finally (8)
I believe the answer is:
educator
'teacher's' is the definition.
(someone who educates)
'disorder cured at hydro finally' is the wordplay.
'disorder' indicates an anagram (a disordered version of the letters).
'finally' says to take the final letters.
The last letter of 'hydro' is 'o'.
'cured'+'at'+'o'='curedato'
'curedato' with letters rearranged gives 'EDUCATOR'.
(Other definitions for educator that I've seen before include "One who teaches others" , "coach" , "Instructor" , "Trainer, teacher" , "school worker" .)