Weak, frail (6)
I believe the answer is:
feeble
I believe this is a double definition.
'weak' is the first definition.
(I know that weak can be written as feeble)
'frail' is the second definition.
(similar in meaning)
(Other definitions for feeble that I've seen before include "Very weak, infirm" , "Wimpish" , "Physically weak or lacking effectiveness" , "Very weak, without strength" , "Weak, frail" .)