Demonstration in support of trial (7)

I believe the answer is:

protest

'demonstration' is the definition.
(I know that demonstration can be written as protest)

'in support of trial' is the wordplay.
'in support of' becomes 'pro' (I've seen this in another clue).
'trial' becomes 'test' (synonyms).
'pro'+'test'='PROTEST'

(Other definitions for protest that I've seen before include "Complaint" , "Express an objection" , "Object loudly" , "Express disagreement" , "Express dissent" .)

I've seen this clue in The Guardian.

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