The most common and most likely answer to this crossword clue is the 3 letter word BRA
B
R
A
More clues leading to the result BRA
Buddy explains!

The straight part
We know that "Cups" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case cups = bra.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 BRA mean?
BRA noun- An item of underwear worn to support the breasts; now commonly shortened to bra.
- One of the two vectors in the standard notation for describing quantum states in quantum mechanics, the other being the ket.
- Friend
- Female version of bro