Figure denoting a number (7)
I believe the answer is:
numeral
'figure denoting a number' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for numeral that I've seen before include "Counting symbol" , "Mathematical figure" , "Symbol representing one or two, perhaps?" , "one involved in maths?" , "1, 2, 3, for instance" .)