Recording medium (4)
'recording medium' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for tape that I've seen before include "Record; material strip" , "Fabric strip; record" , "Record - broken by the winner" , "Measure" , "Music cassette" .)
(Other definitions for audiotape that I've seen before include "recording" , "record" .)