Plant essentially flourishing in weedless ground (9)
I believe the answer is:
edelweiss
'plant' is the definition.
(edelweiss is a kind of plant)
'essentially flourishing in weedless ground' is the wordplay.
'essentially' means to look at the middle letters.
'in' indicates putting letters inside.
'ground' is an anagram indicator ('grind' the letters into a new form).
The central letter of 'flourishing' is 'i'.
'weedless' anagrammed gives 'edelwess'.
'i' going into 'edelwess' is 'EDELWEISS'.
(Other definitions for edelweiss that I've seen before include "I weed less when this flower is around" , "high growth" , "flower as national symbol" , "Swedes lie about small white flower in Switzerland" , "White-flowered alpine plant" .)