Wild disturbance has expert crowd controller (4,3)

I believe the answer is:

riot gun

I'm a little stuck... Click here to teach me more about this clue!

'controller' is the definition.
I know nothing about this answer so I cannot tell whether this works.

'wild disturbance has expert crowd' is the wordplay.
'wild disturbance' becomes 'riot' (I've seen this in another clue).
'has' is a charade indicator (letters next to each other).
'expert crowd' becomes 'gun' (I can't justify this - if you can you should give a lot more credence to this answer).
'riot'+'gun'='RIOT GUN'

Can you help me to learn more?

I've seen this clue in the Sydney Morning Herald.

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