Revolutionary is leading element close to workers' protests (3-3)
I believe the answer is:
sit-ins
'protests' is the definition.
(sit-in is a kind of protest)
'revolutionary is leading element close to workers'' is the wordplay.
'revolutionary' shows that the letters should be reversed in order (letters revolve around).
'leading' means one lot of letters go next to another (some letters go in front of others).
'element' becomes 'tin' (tin is a kind of element).
'close to' suggests the final letters (the 'close' to the word).
The last letter of 'workers' is 's'.
'is' back-to-front is 'si'.
'si'+'tin'+'s'='SIT-INS'
(Other definitions for sit-ins that I've seen before include "Obstructive protests" , "Forms of civil disobedience in which demonstrators refuse to leave a building" , "In these protests, demonstrators refuse to leave a building" .)