The most common and most likely answer to this crossword clue is the 10 plus 5 letter word PARALYMPIC GAMES
I've seen this crossword clue in Independent
P
A
R
A
L
Y
M
P
I
C
G
A
M
E
S
More clues leading to the result PARALYMPIC GAMES
Buddy explains!

The straight part
We know that "active competitions" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case active competitions = paralympic games.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.