Greta trades her soul for unknown European summer house (6)
I believe the answer is:
gazebo
'summer house' is the definition.
(I've seen this before)
'greta trades her soul for unknown european' is the wordplay.
I cannot quite understand how this works, but
'unknown' could be 'z' (algebra) and 'z' is found within the answer.
'her' could be 'gae' and 'gae' is found in the remaining letters.
The remaining letters 'bo' is a valid word which might be clued in a way I don't understand.
This may be the basis of clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for gazebo that I've seen before include "Summer house with a wide view" , "Small garden building for shade and rest" , "Metrical feet" , "Small garden house with a view" , "Summerhouse with views" .)