They were accused of 'spying' for a foreign government.
a 'spy' camera/plane [=a camera/plane used for spying]
a 'spy' novel/thriller [=a novel/thriller about spies]
(..) myself into a small coffin, Lord Varys told me about a queen in the east who... Before I came to power, you favored my brother. All your spies, your little birds, did they tell you Viserys was cruel, stupid, and weak? Would those qualities have made for a good king in your learned opinion? (..)2017 TvShow: Game of Thrones Title: Stormborn Season: 7 Episode 2