Full Idea
A substance is a basic being, something at reality's foundation. What exactly this means is a matter of some controversy. Some philosophers think of substance as an ultimate subject, something that has properties but isn't a property.
Gist of Idea
A substance is, roughly, a basic being or subject at the foundation of reality
Source
David Robb (Substance [2009], 'Intro')
Book Reference
'Routledge Companion to Metaphysics', ed/tr. Le Poidevin/Simons etc [Routledge 2012], p.256
A Reaction
This seems to capture the place of 'substance' in contemporary metaphysics. I think of 'substance' as a placeholder for some threatened account, even in Aristotle.