It's too much working to tie on extra (12)

I believe the answer is:

extortionate

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'it's too much' is the definition.
I can't judge whether this definition defines the answer.

'working to tie on extra' is the wordplay.
'working' indicates an anagram.
'to'+'tie'+'on'+'extra'='totieonextra'
'totieonextra' anagrammed gives 'EXTORTIONATE'.

Can you help me to learn more?

(Other definitions for extortionate that I've seen before include "Outrageous" , "Outrageously costly" , "Very pricey" , "Overly demanding" , "Preposterous" .)

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

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