Wet beam joint in auditorium (5)

I believe the answer is:
rainy
'wet' is the definition.
(similar in meaning)
'beam joint in auditorium' is the wordplay.
I cannot really understand how this works, but
'in' is found in the answer.
'beam' could be 'ray' (synonyms) and 'ray' is found within the leftover letters.
This accounts for all the letters.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for rainy that I've seen before include "Save your money for this damp day" , "Drizzly" , "Save your money for a . . . . . day - to buy an umbrella?" , "Wet, showery" , "Pluvial" .)
