A smashing wave? (7)
I believe the answer is:
breaker
This might be a double definition.
'a smashing' is the first definition.
Although both the answer and definition are singular nouns, I don't see how they can define each other.
'wave?' is the second definition.
(breaker is a kind of wave)
Can you help me to learn more?
(Other definitions for breaker that I've seen before include "Wave hitting the shore" , "Wave with white crest" , "White-topped wave" , "Someone broadcasting on Citizen's Band radio" , "Large sea wave" .)