The shape of cricket in London? (4)
I believe the answer is:
'the shape' is the definition.
(oval is a kind of shape)
'of cricket in london?' is the wordplay.
'of' becomes 'o''.
'cricket in london?' becomes 'val' (I can't explain this - if you can you should believe this answer much more).
Can you help me to learn more?
(Other definitions for oval that I've seen before include "Elliptical figure" , "form of an egg" , "not quite round" , "Cricket ground - presidential office" , "London cricket-ground" .)