The most common and most likely answer to this crossword clue is the 9 letter word PING-PONG
I've seen this crossword clue in The Guardian
P
I
N
G
-
P
O
N
G
Buddy explains!
The straight part
We know that "Being a sport" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case being a sport = ping-pong.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 PING-PONG mean?
PING-PONG noun- Table tennis.
- An instance of figuratively bouncing something or someone back and forth.
- (Parliament) The exchange of proposed amendments between the two houses of parliament, particularly at the end of a session when compromises have to be made to complete the legislative process within the limited time available.
- A size of photograph a little larger than a postage stamp.
- To figuratively bounce or be bounced back and forth.
- To play the game of ping pong.