Hero-worshipper behind Obama, initially, or Bush (8)
I believe the answer is:
oleander
'bush' is the definition.
(oleander is a type of bush)
'hero-worshipper behind obama initially' is the wordplay.
'hero-worshipper' becomes 'leander' (I've seen this before).
'behind' is a charade indicator (letters next to each other).
'initially' says to take the initial letters.
The initial letter of 'obama' is 'o'.
'leander' after 'o' is 'OLEANDER'.
'or' acts as a link.
(Other definitions for oleander that I've seen before include "poisonous plant" , "Poisonous shrub, also called rosebay" , "No leader, oddly, for the flowering shrub" , "Reloaned for evergreen shrub with bright flowers" , "'Adorn eel, badly, with this shrub (8)'" .)