The most common and most likely answer to this crossword clue is the 6 plus 2 plus 7 letter word BATTLE OF BRITAIN
I've seen this crossword clue in Independent
B
A
T
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L
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O
F
B
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More clues leading to the result BATTLE OF BRITAIN
Buddy explains!
The straight part
We know that "Leicester City v Celtic perhaps – or something more serious?" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case leicester city v celtic perhaps – or something more serious? = battle of britain.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.