It was "...a list of notable writers and other persons he considered to be unsuitable as possible writers for the anti-communist propaganda activities..."

https://en.wikipedia.org/wiki/Orwell%27s_list

He gave the list to Celia Kirwan, who said:

"I think George was quite right to do it. ... And, of course, everybody thinks that these people were going to be shot at dawn. The only thing that was going to happen to them was that they wouldn't be asked to write for the Information Research Department."

- these were people Orwell considered Stalinist sympathisers or useful idiots essentially. Orwell of course has fought for POUM and had no truck with Stalinism. They had taken out the POUM leadership in Spain including Andreu Nin who had apparently been been beaten to a pulp by the NKVD / SIM over several days: in his book Stalinists were the enemies of Revolution.

-I once read an account where a number of prisoners taken by SIM were beaten to death with rubber hoses...it reminded me of my friend once telling a story of how his father regularly beat his brother with a washing machine hose pipe...a somewhat barbaric detail that had stuck in my mind.

-It's no coincidence that his father was one of the highest English speaking officers in SIM. It's makes for an interesting night over whisky when you ask one of your best friends if he believed his father was a torturer for Stalin...and he pauses for a long while...then answers: "Yes..."