Makes one's burden a lot greater? (5,2)

I believe the answer is:

loads up

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'makes one's burden' is the definition.
Although both the answer and definition are verbs in their -s form, I cannot understand how one could define the other.

'a lot greater?' is the wordplay.
'a lot' becomes 'load' (both can mean a large amount).
'greater?' becomes 'sup' (I can't explain this - if you can you should believe this answer much more).
'load'+'sup'='LOADS UP'

Can you help me to learn more?

I've seen this clue in the Evening Standard.

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