Useless demonstration of hunger marchers? (5,7)

I believe the answer is:
empty protest
'useless demonstration of hunger marchers?' is the definition.
I can't tell whether this definition defines the answer.
'useless demonstration' is the wordplay.
'useless' becomes 'empty' (I can't justify this - if you can you should believe this answer much more).
'demonstration' becomes 'protest' (I have seen 'Public demonstration ' mean 'protest' so perhaps 'demonstration' could also mean 'protest').
'empty'+'protest'='EMPTY PROTEST'
Can you help me to learn more?
I've seen this clue in The Globe and Mail.
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