Cassette player perhaps found next to class pigeonhole (10)
I believe the answer is:
'pigeonhole' is the definition.
(to pigeonhole is to stereotype)
'cassette player perhaps found next to class' is the wordplay.
'cassette player perhaps' becomes 'stereo' (personal stereo).
'found next to' is a charade indicator (letters next to each other).
'class' becomes 'type' (I've seen this before).
(Other definitions for stereotype that I've seen before include "Conventional image" , "cast" , "received idea?" , "Fixed conventionalised image" , "Spring back (in fear)" .)