Crossword Genius

A dark horse in the field of children’s literature? (5,6)

Ross

I believe the answer is:

black beauty

'a dark horse' is the definition.

I don't understand the remainder of the clue.

(Other definitions for black beauty that I've seen before include "Children's classic about a horse" , "Book by Anna Sewell" .)

I've seen this clue in The Times.
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