Respiratory ailment (6)
I believe the answer is:
asthma
'respiratory ailment' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for asthma that I've seen before include "Distressing breathing condition" , "Breathing problem" , "Distressing ailment affecting breathing" , "Common breathing ailment" , "Chest disorder" .)