What does mean in cockney rhyming slang?

"Mean" in Cockney rhyming slang is a shortened form of "mean and lean", which rhymes with "bean". So, "mean" is slang for "bean".

However, "mean" can also be used as slang for "money", as it rhymes with "queen".

So, depending on the context, "mean" could be referring to either "bean" or "money".