Huge waves ruin man's suit (8)
I believe the answer is:
tsunamis
'huge waves' is the definition.
(I've seen this before)
'ruin man's suit' is the wordplay.
'ruin' is an anagram indicator.
'mans'+'suit'='manssuit'
'manssuit' with letters rearranged gives 'TSUNAMIS'.
(Other definitions for tsunamis that I've seen before include "Huge destructive waves" , "Violent sea waves" , "Destructive sea waves" , "catastrophes" , "Large ocean waves caused by underwater earthquakes" .)