The most common and most likely answer to this crossword clue is the 7 letter word EVERTON
I've seen this crossword clue in The Guardian
E
V
E
R
T
O
N
More clues leading to the result EVERTON
- Liverpool team always getting score of one hundred
- European Green on football team
- Eleven always comes before a hundred
- Tennis champ on football team
- Vertical part shown, cannot reveal side
- Club gets tennis champion further
- Tennis player available for football team
- Tennis player and 15 side 11
- Some cannot reverse backwards in Liverpool
- Retired tennis player writing about footballers
Buddy explains!

The straight part
We know that "side" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case side = everton.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.