. . . heading out of home ground (5)
I believe the answer is:
earth
'ground' is the definition.
(I know that earth is a more specific form of ground)
'heading out of home' is the wordplay.
'heading out of' means to remove the first letter (the letter which heads the word is removed).
'home' becomes 'hearth' (hearth is a kind of home).
'hearth' with its first letter removed is 'EARTH'.
(Other definitions for earth that I've seen before include "electrical safety precaution" , "Human world" , "Mud" , "cost of which is very high" , "Soil; planet" .)