It seems very inconsistent and arbitrary as to whether the theme-word is added to the answer (e.g. 6D), or it or a synonym is removed from the question (e.g., 1D),, or neither (e.g., 3D).
However, I still cannot parse 4A (although it is an anagram of a synonym of the theme-word), 1D (is JC a mushroom?), or 17D (although it's almost there!).
And I have no idea about 14A yet!