The most common and most likely answer to this crossword clue is the 5 letter word LAMPS
I've seen this crossword clue in The Guardian
L
A
M
P
S
More clues leading to the result LAMPS
Buddy explains!

The straight part
We know that "lights" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case lights = lamps.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 LAMPS mean?
LAMPS noun- A device that generates heat, light or other radiation. Especially an electric light bulb.
- A device containing oil, burnt through a wick for illumination; an oil lamp.
- A piece of furniture holding one or more electric light sockets.
- To hit, clout, belt, wallop.
- To hunt at night using a lamp; see lamping.
- To hang out or chill; to do nothing in particular.