The most common and most likely answer to this crossword clue is the 6 letter word CELTIC
I've seen this crossword clue in The Sunday Telegraph
C
E
L
T
I
C
More clues leading to the result CELTIC
- Commons and Lords leaders cite bad language
- Mistakenly let in military leader of druids
- Like 21 across, Scottish football champions 2016-17
- Reportedly dispose of second Scottish club
- Language football team pronounced differently at first
- … Church officer in charge, sort of cross
- Football club cancel tickets for enclosure
- Maybe Scottish Electric’s in liquidation after departure of retiring engineers
- English lieutenant arrested by army chief from Ireland?
- Cancel tickets featuring Boston pro athlete
Buddy explains!

The straight part
We know that "Language football team pronounced differently at first" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case language football team pronounced differently at first = celtic.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.