The most common and most likely answer to this crossword clue is the 5 letter word CAKED
C
A
K
E
D
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The straight part
We know that "Plastered" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case plastered = caked.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.
What does CAKED mean?
CAKED verb- Coat (something) with a crust of solid material.
- To form into a cake, or mass.
- To cackle like a goose.
- (smoking, of a pipe) Empty with nothing left to smoke but ash.