The most common and most likely answer to this crossword clue is the 6 letter word TINKER
I've seen this crossword clue in The Guardian
T
I
N
K
E
R
More clues leading to the result TINKER
- Fiddle one considers not hard
- Mess about with difficult puzzle, not beginning
- Naughty kid‘s fiddle
- Fiddle made from metal by royal couple
- Mess around with one considering ditching husband
- Itinerant‘s fiddle
- Mess around with stone to start with
- Person fixing pot, could be smelly thing with lid lifted
- Little rascal‘s very difficult question head ignored
- One considering getting rid of husband, a rascal
Buddy explains!

The straight part
We know that "Naughty kid/fiddle" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case naughty kid/fiddle = tinker.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 TINKER mean?
TINKER noun- An itinerant tinsmith and mender of household utensils made of metal.
- A member of the Irish Traveller community. A gypsy.
- (usually with "little") A mischievous person, especially a playful, impish youngster.
- Someone who repairs, or attempts repair, on anything mechanical, or who invents such devices; one who tinkers; a tinkerer.
- The act of repair or invention.
- A hand mortar.
- Any of various fish: the chub mackerel, the silverside, the skate, or a young mackerel about two years old.
- A bird, the razor-billed auk.
- To fiddle with something in an attempt to fix, mend or improve it, especially in an experimental or unskilled manner.
- To work as a tinker.
- To tinker with; to tweak or attempt to fix.