The most common and most likely answer to this crossword clue is the 9 letter word RELENTING
I've seen this crossword clue in Financial Times
R
E
L
E
N
T
I
N
G
Buddy explains!

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.
Crossword Answer definitions
RELENTING verb- To become less severe or intense; to become less hard, harsh, or cruel; to soften in temper
- To slacken; to abate.
- To lessen, make less severe or intense.
- (of substance) To become less rigid or hard; to soften; to yield, for example by dissolving or melting
- The act of one who relents.