Infirm (8)
I believe the answer is:
decrepit
'infirm' is the definition.
(I know that infirm can be written as decrepit)
This is the entire clue.
(Other definitions for decrepit that I've seen before include "Run-down by old age or hard use" , "Pet cried (anag) - worn out" , "rickety" , "Dilapidated, made weak by age" , "Depicter in state of dilapidation" .)