It can split area held by expert (7)
I believe the answer is:
cleaver
'it' is the definition.
The definition suggests a singular noun which matches the answer.
'split area held by expert' is the wordplay.
'split area' becomes 'a' (maths abbreviation. I am not sure about the 'split' bit.).
'held by' means one lot of letters goes inside another.
'expert' becomes 'clever' (I've seen this before).
'a' placed into 'clever' is 'CLEAVER'.
'can' is the link.
Can you help me to learn more?
(Other definitions for cleaver that I've seen before include "dangerous object?" , "A clever sort of axe" , "Long-bladed hatchet" , "Meat axe" , "A butcher's chopping tool" .)