18 across
Wine
that’s
often
put
in
a
pocket
(3)
Wine that’s often put in a pocket (3)
hints
0
checks
0
hints
The whole clue is the definition (& lit or double definition).
How the clue works
The whole clue is a Wine that's often put in a pocket, defining RED both as a type of wine and as the snooker ball that is frequently potted into a pocket. There is no separate letter-by-letter wordplay — the clue works as a single whimsical definition.