Girls of nine, perhaps, in a bus (7)
I believe the answer is:
bunnies
'girls' is the definition.
The definition and answer can be both people as well as being plural nouns.
Perhaps you can see a link between them that I don't see?
'nine perhaps in a bus' is the wordplay.
'perhaps' indicates an anagram.
'in' is an insertion indicator.
'nine' is an anagram of 'nnie'.
'nnie' going within 'bus' is 'BUNNIES'.
'of' acts as a link.
Can you help me to learn more?
(Another definition for bunnies that I've seen is " Rabbits".)