Radio and most of cassette player oddly thrown out in error (7,3)
I believe the answer is:
crystal set
'radio' is the definition.
(I've seen this before)
'most of cassette player oddly thrown out in error' is the wordplay.
'most of' means to remove the last letter.
'oddly thrown out' means one should take alternating letters (letters in odd-numbered positions removed).
'in error' indicates anagramming the letters.
The alternating letters of 'player' are 'lyr'.
'cassette' with its last letter taken off is 'cassett'.
'cassett'+'lyr'='cassettlyr'
'cassettlyr' is an anagram of 'CRYSTAL SET'.
'and' acts as a link.
(Other definitions for crystal set that I've seen before include "Radio" , "matching items of glassware?" , "Matching glasses" , "used to receive long ago" , "Receiver" .)