To have a lot on their plate is healthy for politicians (6)
I believe the answer is:
greens
I believe this is a double definition.
'to have a lot on their plate is healthy' is the first definition.
(eat your greens)
'for politicians' is the second definition.
(members of the Green Party)
(Other definitions for greens that I've seen before include "Money" , "those joining in the party" , "Veg" , "identified by little flags" , "Ecology party" .)