Small dog eats large piece of fruit? (4)
I believe the answer is:
pulp
'piece of fruit?' is the definition.
(flesh of a fruit)
'small dog eats large' is the wordplay.
'small dog' becomes 'pup' (short for puppy).
'eats' indicates putting letters inside.
'large' becomes 'L' (eg in clothes sizes).
'pup' going around 'l' is 'PULP'.
(Other definitions for pulp that I've seen before include "Soft, soggy mass" , "Crush" , "Soft plant tissue" , "Soft structureless mass - type of fiction" , "Soft fleshy part of a fruit" .)