Fall away, decline (3)
I believe the answer is:
ebb
I believe this is a double definition.
'fall away' is the first definition.
(I've seen this in another clue)
'decline' is the second definition.
(ebb is a kind of decline)
(Other definitions for ebb that I've seen before include "Tidal retreat" , "Withdraw heartless" , "Fall back" , "Type of tide" , "Drain away; decline" .)