Good entertainer, American guy who gets in the spirit? The opposite! (11)

I believe the answer is:

ghostbuster

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

'gets in the spirit? the opposite' is the definition.
I don't know anything about this answer so I cannot tell whether this works.

'good entertainer american guy' is the wordplay.
'good' becomes 'g' (abbreviation).
'entertainer' becomes 'host' (person hosting or entertaining guests).
'american guy' becomes 'buster' (I can't justify this - if you can you should give a lot more credence to this answer).
'g'+'host'+'buster'='GHOSTBUSTER'

'who' acts as a link.

Can you help me to learn more?

(Another definition for ghostbuster that I've seen is " Poltergeist killer?".)

I've seen this clue in The Guardian.

Want a hint initially instead of a full solution? Install my app