Thrown out when I fill up and fill up dune buggy? (9)

I believe the answer is:

nullified

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'fill up and fill up dune buggy?' is the definition.
I can't tell whether this definition defines the answer.

'thrown out when i' is the wordplay.
'thrown' becomes 'nulled' (I can't explain this - if you can you should believe this answer much more).
'out' indicates putting letters inside.
'when' becomes 'if'.
'if'+'i'='ifi'
'nulled' going around 'ifi' is 'NULLIFIED'.

Can you help me to learn more?

(Other definitions for nullified that I've seen before include "Made invalid" , "revoked" , "Abrogated" , "Scrubbed" , "Cancelled out" .)

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

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