Weakness or infirmity (8)
I believe the answer is:
debility
I believe this clue is a double definition.
'weakness' is the first definition.
(I've seen this before)
'infirmity' is the second definition.
(I know that infirmity can be written as debility)
(Other definitions for debility that I've seen before include "Feebleness, frailty" , "Weakness (from illness)" , "Weakness (of body)" .)