Go away with stepmum mostly playing computer games (5-2-3)

'computer games' is the definition.
I don't know anything about this answer so I cannot tell whether it can be defined by this definition.

'go away with stepmum mostly playing' is the wordplay.
'go away' becomes 'shoo' (I've seen this before).
'with' is a charade indicator (letters next to each other).
'mostly' means to remove the last letter (most but not all of the word).
'playing' is an anagram indicator.
'stepmum' with its last letter taken away is 'stepmu'.
'stepmu' anagrammed gives 'temups'.
'shoo'+'temups'='SHOOT-EM-UPS'

Can you help me to learn more?