The most common and most likely answer to this crossword clue is the 7 letter word SHRINES
I've seen this crossword clue in The Daily Telegraph
S
H
R
I
N
E
S
More clues leading to the result SHRINES
Buddy explains!

The straight part
We know that "tombs" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case tombs = shrines.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 SHRINES mean?
SHRINES noun- A holy or sacred place dedicated to a specific deity, ancestor, hero, martyr, saint, or similar figure of awe and respect, at which said figure is venerated or worshipped.
- A case, box, or receptacle, especially one in which are deposited sacred relics, as the bones of a saint.
- A place or object hallowed from its history or associations.