Greta Thunberg and Isra Hirsi, maybe, with warning (5)
I believe the answer is:
women
'greta thunberg and isra hirsi' is the definition.
I can't tell whether this defines the answer.
'with warning' is the wordplay.
'with' becomes 'w' (abbreviation).
'warning' becomes 'omen' (omen can mean a warning or sign of the future).
'w'+'omen'='WOMEN'
'maybe' acts as a link.
Can you help me to learn more?
(Other definitions for women that I've seen before include "Adult human females" , "half of our race" , "Ladies" .)