The most common and most likely answer to this crossword clue is the 4 letter word UVEA
I've seen this crossword clue in The Daily Telegraph
U
V
E
A
More clues leading to the result UVEA
- Whereby type of light starts to enter animals?
- Bit of a looker going through Villeneuve Airport
- Radiation on each part of the eye
- Luvvie regularly wiped a part of his eye
- Eye partly caught by menu — veal!
- Vague, dizzy, having scratched good part of the eye
- In a certain type of light, each is a bit of a looker
- Ultraviolet exposure initially affects only the front of eye component
- Ultraviolet decay occasionally seen in eye part
Buddy explains!

The straight part
We know that "Eye partly" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case eye partly = uvea.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 UVEA mean?
UVEA noun- The middle of the three concentric layers that make up the eye; it is pigmented and vascular, and comprises the choroid, the ciliary body, and the iris.