Cargo ship carrying quality plant (11)
I believe the answer is:
'plant' is the definition.
(plant of the rose family)
'cargo ship carrying quality' is the wordplay.
'cargo ship' becomes 'coaster' (ship carrying cargo).
'carrying' is an insertion indicator.
'quality' becomes 'tone' (synonyms).
'coaster' placed around 'tone' is 'COTONEASTER'.
(Other definitions for cotoneaster that I've seen before include "Red-berried garden shrub", "Plant", "Shrub with red berries".)