Angry group of proletarians turned up (5)
I believe the answer is:
irate
'angry' is the definition.
(similar in meaning)
'group of proletarians turned up' is the wordplay.
'group of' indicates the answer is hidden within the clue (group of letters from the clue).
'turned up' says the letters should be written backwards.
'etari' is hidden within 'proletarians'.
'etari' backwards is 'IRATE'.
(Other definitions for irate that I've seen before include "Angry, annoyed" , "Not happy" , "will be up in arms" , "Spitting feathers" , "I tear away, being annoyed" .)