He wrote in the evening – standing up in front of his desk surrounded by candles. One of his quirks was to show up at the interval of a play so that everyone thought he’d been out enjoying himself when he’d really not watched the play at all but had been busy at home writing for most of it.
I don't know the the meaning of the word "it" there. Could you explain this to me? And, the word "out" in "he’d been out enjoying himself", I don't understand it too. Is it referring that he'd been outside and enjoyed himself? Thanks