Sonnet delivered great deal (6)

I believe the answer is:

tonnes

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

'sonnet delivered great deal' is the definition.
I can't judge whether this defines the answer.

'sonnet delivered great deal' is the wordplay.
'sonnet' anagrams to 'TONNES'.
But, I'm not clear how the anagram is indicated.

Can you help me to learn more?

(Other definitions for tonnes that I've seen before include "Sent on (anag.)" , "Sonnet about metric weights" , "Weights of 1,000 kilograms" , "1000 kilogram weights" , "Metric tons" .)

I've seen this clue in The Mirror.

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