Lungs not working? Not quite all (5)
I believe the answer is:
offal
'lungs' is the definition.
(offal may be made from lungs)
'not working? not quite all' is the wordplay.
'not working?' becomes 'off' (I've seen this before).
'not quite' means to remove the last letter.
'all' with its last letter taken away is 'al'.
'off'+'al'='OFFAL'
(Other definitions for offal that I've seen before include "Edible (or inedible?) internal organs" , "Heart, liver, kidney etc" , "Refuse - guts" , "Worthless parts of animal carcass" , "Waste matter" .)