Perplex foremost of gardeners, appearing with passion flower (8)
I believe the answer is:
foxglove
'flower' is the definition.
(thesaurus)
'perplex foremost of gardeners appearing with passion' is the wordplay.
'perplex' becomes 'fox' ('fox' can be a synonym of 'perplex').
'foremost of' says to take the initial letters.
'appearing with' is a charade indicator (letters next to each other).
'passion' becomes 'love' ('love' can be a synonym of 'passion'**).
The initial letter of 'gardeners' is 'g'.
'fox'+'g'+'love'='FOXGLOVE'
(Other definitions for foxglove that I've seen before include "Flowering plant that's source of digitalis" , "Common wild flower" , "Plants of the genus Digitalis" , "Tall plant with purple or white flowers - vulpine?" , "that grows wild" .)