Monster Of The Mind loaded on Game Boy (9)

'monster' is the definition.
(boogeyman is a kind of monster)

'of the mind loaded on game boy' is the wordplay.
I cannot really understand how this works, but
'of' could be 'o' and 'o' is found in the answer.
'boy' could be 'bogey' and 'bogey' is present in the leftover letters.
The remaining letters 'man' is a valid word which might be clued in a way I don't see.
This may be the basis of the clue (or it may be nonsense).

Can you help me to learn more?