The most common and most likely answer to this crossword clue is the 6 letter word PUNISH
I've seen this crossword clue in The Guardian
P
U
N
I
S
H
More clues leading to the result PUNISH
- After play on words, is husband fine, say?
- Discipline? Something like a joke, it seems
- Fine maybe after twisting in breaking elbow
- Castigate attempt at humour, to a degree
- Encourage guards in upping discipline
- Crime on the rise, flipping hard to get discipline
- Fine perhaps like some wordplay on the radio
- Play on words is hard to beat
- Push in if it’s out? Correct
- Maybe fine joke is rubbish ultimately
Buddy explains!

The straight part
We know that "discipline" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case discipline = punish.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 PUNISH mean?
PUNISH verb- To cause to suffer for crime or misconduct, to administer disciplinary action.
- To treat harshly and unfairly.
- To handle or beat severely; to maul.
- To consume a large quantity of.