Support the eccentric visionary (7)
I believe the answer is:
prophet
'visionary' is the definition.
(thesaurus)
'support the eccentric' is the wordplay.
'support' becomes 'prop' (prop is a kind of support).
'eccentric' indicates an anagram.
'the' with letters rearranged gives 'het'.
'prop'+'het'='PROPHET'
(Other definitions for prophet that I've seen before include "Visionary" , "reader" , "Soothsayer" , "Divine spokesman or forecaster" , "One who predicts the future" .)