The most common and most likely answer to this crossword clue is the 2 plus 5 plus 6 letter word NO HOLDS BARRED
N
O
H
O
L
D
S
B
A
R
R
E
D
Buddy explains!
The straight part
We know that "without rules" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case without rules = no holds barred.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.