Dancers here are in dances — she may be one of them (9)
I believe the answer is:
ballerina
'dancers here are in dances she may be one of them' is the definition.
Although both the answer and definition are singular nouns, I can't understand how they can define each other.
'dancers here are in dances' is the wordplay.
'dancers here' becomes 'ball' (people dance at a ball).
'dances' is an anagram indicator.
'are'+'in'='arein'
'arein' anagrammed gives 'erina'.
'ball'+'erina'='BALLERINA'
(Other definitions for ballerina that I've seen before include "girl from the Kirov?" , "Female dancer, could be prima" , "lass good at splits?" , "Pavlova?" , "Danseuse" .)