Maximum charge for conveyance (4,4)

I believe the answer is:

full load

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

'maximum charge' is the wordplay.
'maximum' becomes 'full' (I can't justify this - if you can you should believe this answer much more).
'charge' becomes 'load' (loading is a kind of charging).
'full'+'load'='FULL LOAD'

'for' is the link.

Can you help me to learn more?

I've seen this clue in The Globe and Mail.

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