Ogre concealed bloomer (6)
I believe the answer is:
orchid
'bloomer' is the definition.
(I know that orchid is a type of bloomer)
'ogre concealed' is the wordplay.
'ogre' becomes 'orc' (both are horrible fantasy creatures).
'concealed' becomes 'hid' ('hide' can be a synonym of 'conceal').
'orc'+'hid'='ORCHID'
(Other definitions for orchid that I've seen before include "Much sought-after family of plants" , "Exotic bloom" , "Plant with complex blooms" , "Plant with showy flower" , "Do rich have this flower?" .)