Plant obscured by yellow heather (5)
I believe the answer is:
wheat
'plant' is the definition.
(wheat is a kind of plant)
'obscured by yellow heather' is the wordplay.
'obscured by' indicates the answer is hidden within the clue (the answer is hidden or obscured by the clue).
'WHEAT' is hidden in the letters of 'yellow heather'.
(Other definitions for wheat that I've seen before include "cereal's required" , "Cereal crop" , "Hat we turn into grain" , "Field crop" , "staple food" .)