Plant crack on a politician, and heroin, leading to anger (4,8)

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

'a politician and heroin leading to anger' is the wordplay.
I cannot really understand how this works, but
'a' could be 'amp' (A is the symbol for the amp or ampere) and 'amp' is located in the answer.
'heroin' could be 'h' (H is a slang term for heroin) and 'h' is present in the answer.
'anger' could be 'ire' (ire is intense rage) and 'ire' is found in the answer.
The remaining letters 'rocks' 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).

'on' acts as a link.

Can you help me to learn more?