Large amount of earth is turned over in area contaminated with uranium (7)
I believe the answer is:
eurasia
'large amount of earth' is the definition.
(Europe and Asia)
'is turned over in area contaminated with uranium' is the wordplay.
'turned over' indicates an anagram.
'in' indicates putting letters inside.
'contaminated with' indicates an anagram (a corrupted spelling).
'uranium' becomes 'U' (U is the chemical symbol for uranium).
'is' is an anagram of 'si'.
'area' anagrammed with 'u' can make 'euraa'.
'si' placed within 'euraa' is 'EURASIA'.
(Other definitions for eurasia that I've seen before include "Two continents, considered as a whole" , "Continental land mass" , "Largest landmass" , "Land mass - use aria (anag)" , "Landmass extending from Cape Roca in the west to Cape Dezhnev in the east" .)