Flood complete, scarper (7)
I believe the answer is:
overrun
'flood' is the definition.
(I've seen this before)
'complete scarper' is the wordplay.
'complete' becomes 'over' (I've seen this in another clue).
'scarper' becomes 'run' (synonyms).
'over'+'run'='OVERRUN'
(Other definitions for overrun that I've seen before include "Exceed (cost estimate)" , "Exceed time allowed - or conquer territory." , "Inundate, infest" , "Invade - exceed time limit" , "Invade in great numbers" .)