The most common and most likely answer to this crossword clue is the 3 plus 4 letter word LET SLIP
I've seen this crossword clue in The Guardian
L
E
T
S
L
I
P
More clues leading to the result LET SLIP
- Riotous pets I’ll give away
- Accidentally revealed undergarment after cancelled service
- Revealed skill finally on northward ski run, keeping in line
- Don’t keep mum’s “restraint underwear”
- Unintentionally reveal something? Spell it out!
- Making good time, fielder didn’t get to catch
- Permit carried by cricketer without thinking, say
- Tipsily tells one quietly. Blabbed
- Allow cricketer to give the game away
- Give away rental properties before impertinent speech
Buddy explains!
The straight part
We know that "leak" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case leak = let slip.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.