The most common and most likely answer to this crossword clue is the 5 letter word STEIN
S
T
E
I
N
More clues leading to the result STEIN
- Mug in set gets smashed
- Genius Albert, not a German mug!
- European involved in rising fools German mug
- Mug a writer
- Is one in an indefinitely large number a mug?
- Doubles taken from physicist’s mug
- Mug fools about, having drunk last of wine
- In Germany, one can hold one’s drink
- Mug people making pianos? No way!
- Fifth Beatle drops off record for Gertrude?
Buddy explains!

The straight part
We know that "a mug" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case a mug = stein.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 STEIN mean?
STEIN noun- A beer mug, usually made of ceramic or glass.