Despite its name, it's normally neither useful nor amusing! (9,4)
I believe the answer is:
practical joke
'despite its name it's normally neither' is the definition.
I can't tell whether this defines the answer.
'useful nor amusing' is the wordplay.
I cannot quite see how this works, but
'useful' could be 'practical' (similar in meaning) and 'practical' is found within the answer.
The remaining letters 'joke' is a valid word which might be clued in a way I don't understand.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for practical joke that I've seen before include "Unkind prank" , "Prank designed to make a fool of its victim" , "Trick played to discomfort someone" , "rag" , "Jape - hoax" .)