Meaning of "it", "out"

Question

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

Answer 1

One meaning of "be out" is to be "away from home, but not far from home." If you are "out," you are chatting over at the neighbor's or eating at a local restaurant or running errands. If you are in New York but live in Los Angeles, you are "away."

In this case, the meaning is that he had apparently been enjoying himself at the theater rather than working at home. But of course that was not true. He had been working at home on his writing rather than watching actors disporting on the stage. "It" here refers to the play. The antecedent is technically ambiguous because the pronoun does not refer to the immediately preceding noun, but it is the kind of ambiguity that native speakers usually have no trouble resolving. So to rewrite

He wrote in the evening – standing up in front of his desk surrounded by candles. One of his quirks was to show up for only the interval of a play. Thus, everyone thought he’d been out enjoying the play while he actually had been busy writing at home.

Answer 2

"been out enjoying himself" means that he was not home, maybe at a restaurant or a bar, and that he was doing it for fun.

The word 'it' is referring to the time that everyone thought that he was 'out enjoying himself' because that is what was mentioned right before in the sentence.