Plant back without Henry (7)
I believe the answer is:
campion
'plant' is the definition.
(campion is a kind of plant)
'back without henry' is the wordplay.
'back' becomes 'champion' (champion can mean to endorse or back).
'without' is a deletion indicator.
'henry' becomes 'H' (symbol for the unit of electrical inductance).
'champion' with 'h' taken out is 'CAMPION'.
(Other definitions for campion that I've seen before include "Edmund ---, martyr; Thomas ---, poet/lute composer" , "Wild flower (red, white or bladder)" , "Film director" , "Small flower; Thomas -, Elizabethan poet" , "Wayside flower" .)