The most common and most likely answer to this crossword clue is the 8 plus 5 letter word NO-SCORE DRAWS
I've seen this crossword clue in Financial Times
N
O
-
S
C
O
R
E
D
R
A
W
S
Buddy explains!
The straight part
We know that "matches that won’t set the world on fire" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case matches that won’t set the world on fire = no-score draws.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.