Gardener returning to turn over part of the earth (7)
I believe the answer is:
'of the earth' is the definition.
(I've seen this in another clue)
'gardener returning to turn over part' is the wordplay.
'part' indicates the answer is hidden within the clue.
'to turn over' says the letters should be written in reverse.
'enerret' is hidden in the letters of 'gardener returning'.
'enerret' written backwards gives 'TERRENE'.
(Other definitions for terrene that I've seen before include "Of the earth, worldly" , "unearthly? The opposite" , "Earthy" , "of a mundane character" , "region" .)