How would you interpret the last sentence?
Suddenly the waitress was back, unsummoned. “You’re the writer, aren’t you? I’m crazy about your books.”
“What writer?”
“Harrison Shepherd?”
“That’s so strange. You’re the second person to ask me that.”
“Oh. Sorry, my mistake.” She floated away, an unmoored skiff, and disappeared through a door at the back.
Artie reorganized his sigmoidal curve against the bar, the better to stare at his dimwit companion. “What’s wrong with you? She’s a sugar pie.”
“I know it. I’m grateful. To all these girls, I really am.”
“So, you could sign a damn cocktail napkin. It would have made her day.”
“That’s what I can’t see, Artie. What thrilled her was a book—she wants a hero. Not some tin whistle double-gaiter on a barstool.”
“So. In a pinch, you stand in.”

How would you interpret the last sentence: In a pinch, you stand in?
PS: The man was really an author. He and Artie were drinking in a bar.
Thanks! And it’s from The Lacuna.

Question

How would you interpret the last sentence?
Suddenly the waitress was back, unsummoned. “You’re the writer, aren’t you? I’m crazy about your books.”
“What writer?”
“Harrison Shepherd?”
“That’s so strange. You’re the second person to ask me that.”
“Oh. Sorry, my mistake.” She floated away, an unmoored skiff, and disappeared through a door at the back.
Artie reorganized his sigmoidal curve against the bar, the better to stare at his dimwit companion. “What’s wrong with you? She’s a sugar pie.”
“I know it. I’m grateful. To all these girls, I really am.”
“So, you could sign a damn cocktail napkin. It would have made her day.”
“That’s what I can’t see, Artie. What thrilled her was a book—she wants a hero. Not some tin whistle double-gaiter on a barstool.”
“So. In a pinch, you stand in.”

How would you interpret the last sentence: In a pinch, you stand in?
PS: The man was really an author. He and Artie were drinking in a bar.
Thanks! And it’s from The Lacuna.

Answer

He's saying that Shepherd ought to at least pretend to a macho hero so as not to disappoint the waitress.  There is no macho hero, but Shepherd should 'stand in for' him, like an understudy in a film. 'At a pinch' suggests that he isn't a convincing hero, but he might just be able to pass himself off as one if need be.

Answer

"in a pinch" is like "in an emergency" and is used when you need sel thing, but don't have the ideal thing, so you substitute something else. If you're out of buttermilk, in a pinch you can use milk with a spoonful of vinegar instead. She's looking for a hero and Shepherd isn't really a hero, but in a pinch he's the best option she has.