Tape small member of The Mamas and The Papas? (8)
I believe the answer is:
cassette
'tape' is the definition.
(cassette tape is a kind of tape)
I cannot understand how the rest of the clue works.
(Other definitions for cassette that I've seen before include "It may contain film" , "sound equipment" , "Case for reel of magnetic tape" , "Test case (anag.)" , "Box of recordings" .)