Resist work initially with passion in plant (9)
I believe the answer is:
Here is my best explanation:
'plant' is the definition.
(buckwheat is a kind of plant)
'resist work initially with passion' is the subsidiary indication.
'resist' becomes 'buck' (I've seen this before).
'initially' indicates taking the first letters.
'with' is a charade indicator (letters next to each other).
'passion' becomes 'heat' ('heat' can be a synonym of 'passion').
The initial letter of 'work' is 'w'.
'in' is the link.
(Other definitions for buckwheat that I've seen before include "fodder plant", "cereal crop" and "Type of cereal".)