One in five ice cream centres is fruit (6)
I believe the answer is:
quince
'is fruit' is the definition.
(type of fruit)
'one in five ice cream centres' is the wordplay.
'one in five' becomes 'quin' (short for quintuplet).
'ice' becomes 'c' (I am not sure about this - if you are sure you should believe this answer much more).
'centres' says to take the centre.
The middle letter of 'cream' is 'e'.
'quin'+'c'+'e'='QUINCE'
Can you help me to learn more?
(Other definitions for quince that I've seen before include "Acid pear-shaped fruit used in preserves" , "Fruity" , "Acid fruit used in jellies" , "Chips" , "Peter --- (MND); fruit" .)