Oscar and Tim upset with Bundy being forgotten (7)
I believe the answer is:
omitted
'being forgotten' is the definition.
(I've seen this before)
'oscar and tim upset with bundy' is the wordplay.
'oscar' becomes 'O' (phonetic alphabet: alpha, bravo, charlie etc.).
'and' means one lot of letters go next to another.
'upset' is a reversal indicator.
'with' says to put letters next to each other.
'bundy' becomes 'ted' (I can't explain this - if you can you should give a lot more credence to this answer).
'tim' written backwards gives 'mit'.
'o'+'mit'+'ted'='OMITTED'
Can you help me to learn more?
(Other definitions for omitted that I've seen before include "Excluded" , "Cardigan boy" , "Disregarded" , "Musical aptitude" , "Left out, probably forgot" .)