Old number in ragtime there (5)
I believe the answer is:
'old number' is the definition.
(I've seen this in another clue)
'in ragtime there' is the wordplay.
'in' says the answer is hidden in the clue.
'ETHER' is hidden in the letters of 'ragtime there'.
(Other definitions for ether that I've seen before include "Colourless, highly flammable liquid" , "Former anaesthetic" , "Volatile solvent" , "number" , "Type of chemical" .)