Rendered under the influence (9)
I believe the answer is:
plastered
'rendered' is the definition.
(I've seen this before)
I don't understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for plastered that I've seen before include "Drunk (as a ceiling or wall may be)" , "under the table?" , "the worse for drink" , "incapable" , "Might ceilings be" .)