The most common and most likely answer to this crossword clue is the 5 letter word UVEAS
I've seen this crossword clue in Independent
U
V
E
A
S
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The straight part
We know that "Eyeballs somewhat" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case eyeballs somewhat = uveas.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 UVEAS mean?
UVEAS 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.