The most common and most likely answer to this crossword clue is the 3 letter word DIM
I've seen this crossword clue in The Times
D
I
M
More clues leading to the result DIM
- With poor visibility, just over half a kilometre?
- End of crossword – I am needing a bit of illumination?
- Faded image partly indistinct
- Days in March initially quite dark
- Gloomy doctor holds one up
- Not very bright, I’m invested in obsolete currency
- Not clear? Write up its position in grid
- Given dunce’s cap, Knut’s stupid
- Stupid, miles behind inspector
- Short change in America – not bright
Buddy explains!

The straight part
We know that "needing a bit of illumination?" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case needing a bit of illumination? = dim.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 DIM mean?
DIM noun- Dimness.
- To make something less bright.
- To become darker.
- To render dim, obscure, or dark; to make less bright or distinct
- To deprive of distinct vision; to hinder from seeing clearly, either by dazzling or clouding the eyes; to darken the senses or understanding of.
- Not bright or colorful.
- Not smart or intelligent.
- Indistinct, hazy or unclear.
- Disapproving, unfavorable: rarely used outside the phrase take a dim view of.
- Lessened, reduced
- Made to seem less important, impressive, or valuable
- Reduced by a semitone