Sadly, Tim's GST idea was disparaged (11)

I believe the answer is:

stigmatised

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

'disparaged' is the definition.
Both the definition and answer are past participle verbs.
Maybe there's an association between them I don't understand?

'sadly tim's gst idea' is the wordplay.
'sadly' is an anagram indicator.
'tims'+'gst'+'idea'='timsgstidea'
'timsgstidea' with letters rearranged gives 'STIGMATISED'.

'was' is the link.

Can you help me to learn more?

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

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