Fruit served initially with fish (8)
I believe the answer is:
shaddock
'fruit' is the definition.
(shaddock is a kind of fruit)
'served initially with fish' is the wordplay.
'served initially' becomes 'dock' (I can't justify this - if you can you should give a lot more credence to this answer).
'with' means one lot of letters go next to another.
'fish' becomes 'shad' (shad is a kind of fish).
'dock' put after 'shad' is 'SHADDOCK'.
Can you help me to learn more?
(Other definitions for shaddock that I've seen before include "Tropical fruit" , "Citrus fruit" , "tree" , "Pomelo" .)