Fruit shows the extent of the circle (6)
I believe the answer is:
orange
'fruit' is the definition.
(I know that orange is a type of fruit)
'the extent of the circle' is the wordplay.
I cannot quite understand how this works, but
'extent' could be 'range' (range is a kind of extent) and 'range' is present in the answer.
'of' could be 'o' and 'o' is located in the answer.
This accounts for all the letters.
This explanation may well be incorrect...
'shows' is the link.
Can you help me to learn more?
(Other definitions for orange that I've seen before include "A rainbow colour" , "Royal house - fruit - colour" , "stocking filler" , "Go earn the fruit" , "Type of fruit from which bergamot comes" .)