Pasta mostly effective in hoop shapes (10)
I believe the answer is:
tortellini
'pasta' is the definition.
(I know that tortellini is a type of pasta)
'mostly effective in hoop shapes' is the wordplay.
'mostly' means to remove the last letter (most but not all of the word).
'effective' becomes 'telling' (similar in meaning).
'in' means one lot of letters goes inside another.
'hoop shapes' becomes 'tori' (I can't justify this - if you can you should believe this answer much more).
'telling' with its last letter removed is 'tellin'.
'tellin' going within 'tori' is 'TORTELLINI'.
Can you help me to learn more?
(Other definitions for tortellini that I've seen before include "Small filled pasta cases" , "Italian dish" , "Rings for food" , "pasta dish" , "Pasta is called for" .)