Covered in flowers left in a flourish (6)
I believe the answer is:
abloom
'covered in flowers' is the definition.
'left in a flourish' is the wordplay.
'left' becomes 'l' (common abbreviation).
'in' is an insertion indicator.
'flourish' becomes 'boom' ('boom' can be a synonym of 'flourish').
'a'+'boom'='aboom'
'l' put within 'aboom' is 'ABLOOM'.
(Other definitions for abloom that I've seen before include "covered in flowers?" , "Healthy" , "full of colour" , "In flower" , "Flourishing" .)