Environmentalist Brockovich (4)
I believe the answer is:
erin
'environmentalist brockovich' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for erin that I've seen before include "Let ... Remember (song)" , "Early and poetic name here" , "country" , "Poetically, Ireland" , "(Literary name for) Ireland" .)