Flood foiler (5)
I believe the answer is:
levee
'flood foiler' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for levee that I've seen before include "Early morning reception by a monarch" , "Embankment on the Mississippi" , "Artificial embankment" , "Gathering" , "Morning reception once held by monarch" .)