In a detailed manner ask the man his complaint (6)
I believe the answer is:
asthma
'complaint' is the definition.
(asthma is a kind of disease)
I can't explain the remainder of the clue.
Can you help me to learn more?
(Other definitions for asthma that I've seen before include "Respiratory illness" , "inspiring trouble" , "Distressing ailment affecting breathing" , "Bronchial allergy" , "Breathing complaint" .)