The most common and most likely answer to this crossword clue is the 8 letter word BIFOCALS
I've seen this crossword clue in The Daily Telegraph
B
I
F
O
C
A
L
S
More clues leading to the result BIFOCALS
Buddy explains!

The straight part
We know that "glasses" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case glasses = bifocals.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 BIFOCALS mean?
BIFOCALS noun- Spectacles that have corrective lenses of two different powers; used by people who need both distance and reading glasses.