Sag, wilt (5)
I believe the answer is:
droop
This clue is a double definition.
'sag' is the first definition.
(I know that sag can be written as droop)
'wilt' is the second definition.
(I know that wilt can be written as droop)
(Other definitions for droop that I've seen before include "Sag, hang down" , "Hang downwards, lose strength or spirit" , "lose heart" , "Sag downwards" , "sink" .)