PC gone mad? This may be why (7)
I believe the answer is:
malware
'pc gone mad? this' is the definition.
I don't know anything about this answer so I can't tell whether it can be defined by this definition.
'be why' is the wordplay.
I cannot really understand how this works, but
'be' could be 'are' (I've seen this in another clue) and 'are' is found in the answer.
This may be the basis of the clue (or it may be nonsense).
'may' acts as a link.
Can you help me to learn more?
(Another definition for malware that I've seen is " Pernicious computer programs".)