Murderous creatures concealed inside flowers (7)
I believe the answer is:
orchids
'flowers' is the definition.
(orchid is a kind of flower)
'murderous creatures concealed inside' is the wordplay.
'murderous creatures' becomes 'orcs' (I can't explain this - if you can you should believe this answer much more).
'concealed' becomes 'hid' ('hide' can be a synonym of 'conceal').
'inside' is an insertion indicator.
'orcs' placed around 'hid' is 'ORCHIDS'.
Can you help me to learn more?
(Other definitions for orchids that I've seen before include "Highly prized plants" , "Chords I turn into flowers" , "Glamorous tropical flowers" , "Flowers from a rich sod" , "Showy plants" .)