The most common and most likely answer to this crossword clue is the 3 letter word WIT
I've seen this crossword clue in Financial Times
W
I
T
Buddy explains!
The straight part
We know that "humour" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case humour = wit.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 WIT mean?
WIT noun- (now usually in the plural) Sanity.
- (obsolete usually in the plural) The senses.
- Intellectual ability; faculty of thinking, reasoning.
- The ability to think quickly; mental cleverness, especially under short time constraints.
- Intelligence; common sense.
- Humour, especially when clever or quick.
- A person who tells funny anecdotes or jokes; someone witty.
- Know, be aware of (constructed with of when used intransitively).
- Against.
- In the company of; alongside, close to; near to.
- In addition to; as an accessory to.
- Used to indicate simultaneous happening, or immediate succession or consequence.
- In support of.
- In regard to.
- To denote the accomplishment of cause, means, instrument, etc; – sometimes equivalent to by.
- Using as an instrument; by means of.
- Using as nourishment; more recently replaced by on.
- Having, owning.
- Affected by (a certain emotion or condition).
- Prompted by (a certain emotion).