A cross for ten in ancient Rome, say? (7)
I believe the answer is:
numeral
This clue could be a double definition.
'a cross' is the first definition.
Although both the answer and definition are singular nouns, I can't see how one could define the other.
'ten in ancient rome say?' is the second definition.
Although both the answer and definition are singular nouns, I can't see how one could define the other.
'for' is the link.
(Other definitions for numeral that I've seen before include "Symbol representing one or two, perhaps?" , "Symbol used to express quantity" , "Mathematical figure" , "Counting symbol" , "1, 2, 3, say" .)