The most common and most likely answer to this crossword clue is the 8 letter word ORDINALS
I've seen this crossword clue in The Guardian
O
R
D
I
N
A
L
S
Buddy explains!

The straight part
We know that "Numbers" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case numbers = ordinals.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 ORDINALS mean?
ORDINALS noun- An ordinal number such as first, second and third.
- A book used in the ordination of Anglican ministers, or in certain Roman Catholic services