Hilda unsettled by a bloomer (6)
I believe the answer is:
dahlia
'bloomer' is the definition.
(dahlia is a kind of flowering plant)
'hilda unsettled by a' is the wordplay.
'unsettled' indicates an anagram.
'by' means one lot of letters go next to another.
'hilda' with letters rearranged gives 'dahli'.
'dahli'+'a'='DAHLIA'
(Other definitions for dahlia that I've seen before include "Suggestive of soil" , "Lia had this flower, strangely" , "one in bed" , "Lia had this strange flower" , "Showy, big-headed autumn flower" .)