The most common and most likely answer to this crossword clue is the 3 plus 3 letter word LET OFF
I've seen this crossword clue in Independent
L
E
T
O
F
F
More clues leading to the result LET OFF
Buddy explains!
The straight part
We know that "Be lenient/light" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case be lenient/light = let off.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 LET OFF mean?
LET OFF noun- An escape from punishment.
- A device for letting off, releasing, or giving forth, as the warp from the cylinder of a loom.