Part of dear Earth (4)
I believe the answer is:
Here is my best explanation:
'part' is the definition.
(area is a kind of part)
'of dear earth' is the subsidiary indication.
'of' says the answer is hidden in the clue.
'area' can be found hidden inside 'dear earth'.
(Other definitions for area that I've seen before include "Succession, order", "Surface measurement", "Length multiplied by breadth", "Expanse or neighbourhood", "Extent of a two-dimensional surface", "'Tract, region (4)'", "Extent of a 2-dimensional surface", "Space for a specific purpose, say picnic", "Region; extent of a surface" and "Field of activity or surface".)