The most common and most likely answer to this crossword clue is the 8 letter word PANNIKIN
I've seen this crossword clue in The Times
P
A
N
N
I
K
I
N
More clues leading to the result PANNIKIN
Buddy explains!

The straight part
We know that "Small cup" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case small cup = pannikin.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 PANNIKIN mean?
PANNIKIN noun- A durable cup or other vessel used for drinking made of metal and coated in enamel.
- The contents of such a vessel.