Figure on almost erect figure (9)
I believe the answer is:
rectangle
'figure' is the definition.
(rectangle is a kind of figure)
'on almost erect figure' is the wordplay.
'on' says to put letters next to each other.
'almost' means to remove the first letter.
'figure' becomes 'angle' (I can't justify this - if you can you should give a lot more credence to this answer).
'erect' with its first letter taken away is 'rect'.
'rect'+'angle' is 'RECTANGLE'.
Can you help me to learn more?
(Other definitions for rectangle that I've seen before include "Four-sided figure" , "Shape of football pitch" , "Quadrilateral" , "Figure on plane" , "regular sort of figure" .)