A film review reads:
An accepted conceit in Hollywood, and amongst world leaders engaged with reality, is that our time on Earth is at risk of running out. In other words, "heroes required - apply within". One of the most intriguing heroes of recent year - on the fictional side of things at least - is Matthew McConaughey's Cooper in Christopher Nolan's 2014 smash Interstellar.
What does "heroes required - apply within" mean here? I feel like it is used in a whimsical tone but I do not exactly know what it is referring to. In particular, dictionaries suggest that "apply within" means
to ask about something [inside some place]
How is it applied in this context? Aside from that, I am also not quite sure about the meaning of "conceit" here. The definition of it is:
an ingenious or fanciful comparison or metaphor.
Is the author suggesting that "The Earth is at a risk of running out" is an ingenious idea in Hollywood? I am not quite sure about that because it seems to be a very common idea.
As a side note, I haven't watched the Interstellar before, if that matters. Thanks in advance.