The most common and most likely answer to this crossword clue is the 4 letter word TWOS
I've seen this crossword clue in The Daily Telegraph
T
W
O
S
Buddy explains!

The straight part
We know that "Four of these may be found in eight" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case four of these may be found in eight = twos.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 TWOS mean?
TWOS noun- The digit/figure 2.
- A two-dollar bill.
- A child aged two.
- A playing card featuring two pips.
- A pair of twos.
- A reserves team.
- To share a cigarette with someone after smoking half of it.