The most common and most likely answer to this crossword clue is the 4 plus 4 letter word POLE STAR
I've seen this crossword clue in The Times
P
O
L
E
S
T
A
R
More clues leading to the result POLE STAR
- Pulsing laser, top guide at night
- European sailor clutching second leading light?
- European celebrity finding direction indicator?
- European * leader?
- Leader of visible magnitude, apostle converted unbeliever, finally
- Leading light from Staffs turned traitor
- Pastor worked up about the French heavenly guide
- European sailor welcomes bearing from this guide
- Navigational aid provided by some Europeans sailor follows
- Sailor punts first as a guide
Buddy explains!

The straight part
We know that "guide at night" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case guide at night = pole star.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.