Thanks guys! Put it down to thinking too hard - my excuse.
I'd logged off after posting my query and this morning, while shaving and not thinking about it, a little grey cell lit up and to my SHEER, TOTAL embarrassment I twigged! "D'oh!" What a twit I felt.
Later I checked back through my Thesaurus (good ol' paperback) and, typically, last night, when trying too hard with tunnel vision, I missed it.
I'd searched under "total" which led me to "32 Largeness" - and then "consummate" - BUT no "sheer" - that little tinker was in the paragraph immediately below under "absolute"!
Put it down to advancing years, but nowadays a crossword at first looks impossible but when I return a day or two later things start to fall into place.
Morse would have had no competition from me!
Well! That's that off my chest - and thanks again.