The closest thing is to set all the variables in Main to nothing, which will allow their memory to be freed.
See e.g. How to clear variables and/or whole work space - #27 by heliosdrm or this one-liner:
setproperty!.((Main,), filter(n -> !isconst(Main, n), names(Main)), nothing);
but this doesn’t eliminate constants, including function definitions and new methods, or other global state that might be affecting your code.