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]
(..) - A friend? - An enemy. Oh. Which one? Well, your arch-enemy, according to him. Do people have arch-enemies? Did he offer you money to spy on me? - Yes. - Did you take it? - No. - Pity, we could have split the fee. - Think it through next time. (..)2010 TvShow: Sherlock Title: A Study in Pink Season: 1 Episode 1