Classical composition from Brahms, on a tape (6)
I believe the answer is:
sonata
'classical composition' is the definition.
(I've seen this before)
'from brahms on a tape' is the wordplay.
'from' says the answer is hidden in the clue.
'SONATA' can be found hidden inside 'brahms on a tape'.
(Other definitions for sonata that I've seen before include "Solo instrumental composition" , "Type of musical composition" , "To NASA, strangely, for the solo piece" , "just for one or two players?" , "musical performance" .)