The police officer walked through the neighborhood, 'keeping a' (sharp) 'lookout for' any suspicious activity.
The police are 'on the lookout for' two men who escaped from custody yesterday.
If he wants to spend all his money on expensive clothes, that's 'his lookout'.
(..) - You said "minkey." - That is correct, yes. Chimpanzee monkey. So I let them both off with a warning. The beggar was the lookout man for the gang. - That is impossible. - Why? He was blind. How can a blind man be a lookout? How can an idiot be a policeman? (..)1975 The Return of the Pink Panther