Letter expected answer (4)
I believe the answer is:
beta
'letter' is the definition.
(I know that beta is a type of letter)
'expected answer' is the wordplay.
'expected' becomes 'bet' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'answer' becomes 'a' (abbreviation eg in Q and A).
'bet'+'a'='BETA'
Can you help me to learn more?
(Other definitions for beta that I've seen before include "2nd letter of Greek alphabet" , "sort of test" , "Second-class" , "Character between alpha and gamma" , "Second-rate" .)