A half turn repeated, often seen in ballet (4)
I believe the answer is:
tutu
'often seen in ballet' is the definition.
Although both the answer and definition are singular nouns, I can't see how one could define the other.
'a half turn repeated' is the wordplay.
'a half' suggests halving the letters.
'repeated' indicates the doubling of some letters.
'turn' with half the letters taken is 'tu'.
'tu' duplicated is 'TUTU'.
Can you help me to learn more?
(Other definitions for tutu that I've seen before include "Ballerina's stiff skirt" , "very short garment" , "A ballerina's short skirt" , "In which dancer may appear" , "Giselle's skirt" .)