Lumen - correct, all entries are non-words barring luck. Word play is normal, other than the extra word to be determined and removed.
I can only go by my experience, and that is that having cold solved not too many (probably 10 or so) I started to spot the features that the omitted words spelled out, which are all of a thematic kind, which in turn helped solve more by knowing which other words were extras.
The entries which are a letter too long for their space are the most helpful, as when they intersect they give you a way in. It is tough but not impossible and dogged determination got me there eventually, whether you decide it isn't worth bothering is down to you. Personally I hate being beaten and have time in abundance. Good luck!