Eminence of Henry first to last – last Henry being that (6)
I believe the answer is:
eighth
'last last henry being that' is the definition.
The definition and answer can be both quantities as well as being singular nouns.
Perhaps they are linked in a way I don't understand?
'eminence of henry first' is the wordplay.
'eminence of' becomes 'eight' (I can't justify this - if you can you should believe this answer much more).
'henry first' becomes 'h' (est letter of 'henry').
'eight'+'h'='EIGHTH'
'to' acts as a link.
Can you help me to learn more?
(Other definitions for eighth that I've seen before include "Real fraction" , "Ordinal number; octave" , "Twelve and a half percent" , "One after seventh" , "Half a quarter" .)