Green plant round field regularly makes fodder (6)
I believe the answer is:
silage
'fodder' is the definition.
(fodder used to feed animals)
'green plant round field regularly' is the wordplay.
'green plant' becomes 'sage'.
'round' indicates putting letters inside.
'regularly' indicates alternate letters (regularly take one letter, leave next etc.).
The alternating letters of 'field' are 'il'.
'sage' going around 'il' is 'SILAGE'.
'makes' is the link.
(Other definitions for silage that I've seen before include "Animal feed" , "Form of fodder" , "Animal fodder harvested while green and partially fermented" , "Partially fermented grass fodder" , "Crop harvested for fodder" .)