I could find only one word which would fit for 4 A - by that point I had six of the ten letters. (the reference to 'definitions in Chambers ' applies to the two words spelled out by the extra letters - I didn't bother with that bit!)
ehf - if you have found the two 8 letter words, you need a defn common to both. Then 4a and all the other unclued are examples of this defn. If you haven't got the defn, then look at the unclued ones( or the letters you have so far for them - some of them have only 1 possibility) and you should notice a common pattern to them all. Then remember to highlight the said defn