The most common and most likely answer to this crossword clue is the 4 letter word GLOW
I've seen this crossword clue in The Times
G
L
O
W
More clues leading to the result GLOW
Buddy explains!

The straight part
We know that "light" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case light = glow.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 GLOW mean?
GLOW noun- The state of a glowing object.
- The condition of being passionate or having warm feelings.
- The brilliance or warmth of color in an environment or on a person (especially one's face).
- To give off light from heat or to emit light as if heated.
- To radiate some emotional quality like light.
- To gaze especially passionately at something.
- To radiate thermal heat.
- To shine brightly and steadily.
- To make hot; to flush.
- To feel hot; to have a burning sensation, as of the skin, from friction, exercise, etc.; to burn.