Supporter with general backing when accepted (5)
I believe the answer is:
easel
'supporter' is the definition.
'general backing when accepted' is the wordplay.
'general' becomes 'Lee' (Robert E. Lee - US revolutionary commander).
'backing' says the letters should be written in reverse.
'when' becomes 'as' (eg 'when I walked' means 'as I walked').
'accepted' is an insertion indicator.
'lee' backwards is 'eel'.
'eel' enclosing 'as' is 'EASEL'.
'with' acts as a link.
(Other definitions for easel that I've seen before include "Picture stand" , "Artistic support" , "Stand used by artists" , "board support" , "supporter of the arts" .)