Son and I can second protests (3-3)
I believe the answer is:
sit-ins
'protests' is the definition.
(sit-in is a kind of protest)
'son and i can second' is the wordplay.
'son' becomes 's' (genealogical abbreviation for son).
'and' is a charade indicator (letters next to each other).
'can' becomes 'tin' (synonyms).
'second' becomes 's' (common abbreviation).
's'+'i'+'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" .)