Large sea wave (6)
'large sea wave' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for tsunami that I've seen before include "Large ocean wave" , "Large sea wave caused by an earthquake" , "Seismic sea wave" , "Huge tidal wave that causes great damage and loss of life" , "Strong surge" .)
'large sea wave' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for breaker that I've seen before include "Wave with white crest" , "White-topped wave" , "Heavy wave arriving on the shore" , "one stopping, might you say?" , "Wave hitting the shore" .)
(Other definitions for billow that I've seen before include "Surge" , "Swell out (as a sail)" , "Swell out, as a flag" , "Become inflated; rise up, as in waves" , "Rise or roll like wave" .)