Apple, America decided should support Republican (6)
I believe the answer is:
russet
'apple' is the definition.
(a russet-coloured apple)
'america decided should support republican' is the wordplay.
I cannot quite see how this works, but
'america' could be 'us' (United States) and 'us' is found in the answer.
'decided' could be 'set' (I've seen this in another clue) and 'set' is present in the answer.
'republican' could be 'r' (abbreviation) and 'r' is found within the answer.
This accounts for all the letters.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for russet that I've seen before include "browny-red" , "Autumnal reddish brown" , "Autumnal reddish-brown colour" , "Apple - colour" , "Autumn red" .)