Horribly wet — a valid reason? (5,4)
I believe the answer is:
tidal wave
'reason?' is the definition.
Although both the answer and definition are singular nouns, I cannot see how one could define the other.
'horribly wet a valid' is the wordplay.
'horribly' indicates anagramming the letters (a horribly wrong version of the letters).
'wet'+'a'+'valid'='wetavalid'
'wetavalid' anagrammed gives 'TIDAL-WAVE'.
Can you help me to learn more?
(Other definitions for tidal wave that I've seen before include "Very powerful movement (at sea?)" , "Overwhelming surge" , "Huge movement of public opinion" , "potential disaster, naturally" , "Large movement (of water or public opinion)" .)