One in US area possibly, or much bigger area (7)
I believe the answer is:
eurasia
'much bigger area' is the definition.
'eurasia' can be an answer for 'area' (I have seen 'Huge area' mean 'eurasia' so perhaps 'area' could also mean 'eurasia'). I am not sure about the 'much bigger' bit.
'one in us area possibly' is the wordplay.
'one' becomes 'i' (Roman numeral).
'in' indicates putting letters inside.
'possibly' is an anagram indicator.
'us'+'area'='usarea'
'usarea' with letters rearranged gives 'eurasa'.
'i' placed inside 'eurasa' is 'EURASIA'.
'or' acts as a link.
Can you help me to learn more?
(Other definitions for eurasia that I've seen before include "Landmass extending from Cape Roca in the west to Cape Dezhnev in the east" , "Large expanse of land" , "Turkey, and so on" , "Germany and Japan are in it" , "Two continents considered as one" .)