Main goal is shaping flowering shrub (8)
I believe the answer is:
magnolia
'flowering shrub' is the definition.
(type of flowering plant)
'main goal is shaping' is the wordplay.
'is shaping' indicates anagramming the letters.
'main'+'goal'='maingoal'
'maingoal' anagrammed gives 'MAGNOLIA'.
(Other definitions for magnolia that I've seen before include "Fragrant blooms might strangely gain loam" , "Tree with showy flowers" , "Mississippi, the ___ State - tree or shrub" , "Flowering tree; light pinkish white" , "pale colour" .)