The most common and most likely answer to this crossword clue is the 7 letter word ORDINAL
I've seen this crossword clue in The Times
O
R
D
I
N
A
L
More clues leading to the result ORDINAL
- Perhaps first or second of animals entering ring
- What's to be said about unwanted noise first, say
- Second, perhaps, to have spoken about loud noise
- Rod left in a split second, maybe
- E.g. third service book
- What’s first? It’s filling crossword in, always
- Service book from Ford in a library
- Uproar during exam leads to third for one
- It may be first spoken without much sound
- Eg second line installed for railway in common
Buddy explains!

The straight part
We know that "Perhaps first" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case perhaps first = ordinal.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 ORDINAL mean?
ORDINAL 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
- (of a number) indicating position in a sequence
- Of or relating to the groupings called orders
- Intercardinal