The most common and most likely answer to this crossword clue is the 8 letter word BAKELITE
B
A
K
E
L
I
T
E
Buddy explains!
The straight part
We know that "Plastic" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case plastic = bakelite.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 BAKELITE mean?
BAKELITE noun- A heat-resisting chemically inert phenol formaldehyde resin (an early thermosetting plastic).