The most common and most likely answer to this crossword clue is the 13 letter word ENTERTAINMENT
I've seen this crossword clue in The Daily Telegraph
E
N
T
E
R
T
A
I
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M
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T
More clues leading to the result ENTERTAINMENT
- Teen entrant I’m playing for fun
- At Internet, men's unexpected fun?
- Doctors treat nine men before start of the fun
- Go into main tent prepared for show
- Show people confined by record contagion
- Record contagion restricting people’s fun
- Access item, an awfully good book — fun!
- … natter with eminent lunatic provides amusement
- Prepare to watch circus, including bizarre main show
- Show diversion
Buddy explains!

The straight part
We know that "amusement" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case amusement = entertainment.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 ENTERTAINMENT mean?
ENTERTAINMENT noun- An activity designed to give pleasure, enjoyment, diversion, amusement, or relaxation to an audience, no matter whether the audience participates passively as in watching opera or a movie, or actively as in games.
- A show put on for the enjoyment or amusement of others.
- Maintenance or support.
- Admission into service; service.
- Payment of soldiers or servants; wages.
- Reception; (provision of) food to guests or travellers.