deslyxic - I believe that Azed has worked on the premise that a particular entry 'belongs' to the word of which it contains the first half - so the unmodified answer to 18ac is GHEE, with the second half then being replaced by the second half of REDO. The instructions and recommended solving method are based on that concept. However, there is a symmetry to the entire puzzle which means that one could equally view the 'site owner' as the word whose second half appears there, so 18ac starts off as REDO, with the initial pair of letters being replaced by the first half of GHEE. What that means is that having solved 18ac the solver has opened up two chains rather than one - they can look (as Azed suggests) for another definition of GHEE, but in addition they can seek out the other definition of REDO.
And yes, I am very glad that I no longer submit clues for the competition! The key, I suspect, will be the selection of at least one definition which is somewhat oblique.