Wise up, say, rejecting dope and smack (3,4,2)

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

'rejecting dope and smack' is the wordplay.
'rejecting' becomes 'ge' (I can't justify this - if you can you should give a lot more credence to this answer).
'dope' becomes 'twit' (both can mean a stupid person).
'and' is a charade indicator (letters next to each other).
'smack' becomes 'hit' (I've seen this in another clue).
'ge'+'twit'+'hit'='GET WITH IT'

'say' acts as a link.

Can you help me to learn more?