Flood ruins exotic hotel (6)
I believe the answer is:
inrush
'flood' is the definition.
(I've seen this in another clue)
'ruins exotic hotel' is the wordplay.
'exotic' indicates anagramming the letters (an unusual form of the letters).
'hotel' becomes 'h' (phonetic alphabet: alpha, bravo, charlie etc.).
'ruins' with letters rearranged gives 'inrus'.
'inrus'+'h'='INRUSH'
(Other definitions for inrush that I've seen before include "Sudden arrival (of people or water?)" , "Overwhelming flow" , "Inflow" , "Internal thrust" , "Sudden influx" .)