Good with numbers (8)
I believe the answer is:
numerate
'good with numbers' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for numerate that I've seen before include "Understanding arithmetic" , "Able to work with numbers - tell" , "Able to do arithmetic" , "Good at sums and maths" , "Able to count, work with figures" .)