The most common and most likely answer to this crossword clue is the 4 letter word TAME
I've seen this crossword clue in The Guardian
T
A
M
E
More clues leading to the result TAME
- Part of operetta, mediocre, uninspiring
- Sent a message about pet
- Dull carpeting returned by European
- Unexciting team lost
- Cultivated part of flower, trimming both sides
- Master sped away from amazing stampede
- Break in length of clematis needs cutting back
- Cheers setter without vigour
- Broken team would be —-_
- Gentle hint, a member assumes
Buddy explains!

The straight part
We know that "Gentle" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case gentle = tame.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.
What does TAME mean?
TAME verb- To make (an animal) tame; to domesticate.
- To become tame or domesticated.
- To make gentle or meek.
- Not or no longer wild; domesticated
- (chiefly of animals) Mild and well-behaved; accustomed to human contact
- Not exciting.
- Crushed; subdued; depressed; spiritless.
- (of a knot) Capable of being represented as a finite closed polygonal chain.
- To broach or enter upon; to taste, as a liquor; to divide; to distribute; to deal out.