Dance costume pronounced excessively dated (4)
I believe the answer is:
tutu
'dance costume' is the definition.
(skirt worn in ballet)
'pronounced excessively dated' is the wordplay.
'pronounced' shows a homophone (sound like).
'excessively dated' becomes 'too-too' (dated term meaning excessive or excessively).
'tootoo' is a homophone of 'TUTU'.
(Other definitions for tutu that I've seen before include "8 [BALLET] term" , "very short garment" , "Short dress" , "Archbishop Desmond" , "Female ballet costume" .)