The most common and most likely answer to this crossword clue is the 9 letter word FORETELLS
I've seen this crossword clue in The Times
F
O
R
E
T
E
L
L
S
Buddy explains!

The straight part
We know that "sees ahead" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case sees ahead = foretells.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 FORETELLS mean?
FORETELLS verb- To predict; to tell (the future) before it occurs; to prophesy.
- To tell (a person) of the future.