The most common and most likely answer to this crossword clue is the 5 plus 4 letter word EARTH SIGN
I've seen this crossword clue in The Times
E
A
R
T
H
S
I
G
N
More clues leading to the result EARTH SIGN
Buddy explains!

The straight part
We know that "The Bull, perhaps" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case the bull, perhaps = earth sign.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.