The phrase "activist inside the" is not complete and lacks context, but it is grammatically correct and can be used in written English.
You can use it when referring to someone who is an activist within a specific organization, movement, or context.
Example: "She is an activist inside the environmental movement, advocating for sustainable practices."
Alternatives: "activist within the" or "activist in the".
Perhaps Bono, who has spent years persuading the world that there's an activist inside of each and every one of us, should set aside his pride and give the protesters in the crowd a cheer.
Armed activists were inside the building during the session.
Late one night, he and several other Salafiyya activists slipped inside the charity.
Following the activists inside, some headed straight to the departure boards, while others made a beeline for the MAC Cosmetics shop.
Rami Jarrah, who coordinates the efforts of a network of video activists inside Syria from Cairo, drew attention to clips of protesters rallying outside the police headquarters on Khaled Ibn Al Walid Street in Damascus, and then fleeing from gunfire.
Activists inside the chamber cheered and waved rainbow banners, scenes repeated outside as news spread.
Rebels and activists inside the city said the fighting for the complex began late Friday with a rebel assault.
The monitoring group, which relies on a network of activists inside the country, said Islamic State fighters have executed and paraded the bodies of "tens" of soldiers in the northern city of Raqqa, the only provincial capital in rebel hands.
Contact was then made with Syrian activists inside the country, and go-betweens recruited, notably Wissam Tarif, a highly respected Syrian pro-democracy leader who is widely consulted by journalists and senior western diplomats.
He suggested that the Iranian government planned to create fake sites that would fool activists inside the country into thinking they were on a secure site which could not be tapped, but instead would collect their details.
