The most common and most likely answer to this crossword clue is the 11 letter word LIGHTHOUSES
I've seen this crossword clue in The Sunday Telegraph
L
I
G
H
T
H
O
U
S
E
S
Buddy explains!
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 LIGHTHOUSES mean?
LIGHTHOUSES noun- A tower or other structure exhibiting a light or lights to warn or guide sailors.