Food preparation is part of the service (4)
I believe the answer is:
dish
'the service' is the definition.
(thesaurus)
'food preparation is part' is the wordplay.
'food preparation' becomes 'dh' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'part' means one lot of letters goes inside another (the inserted letters split open or part the word).
'dh' going around 'is' is 'DISH'.
'of' is the link.
Can you help me to learn more?
(Other definitions for dish that I've seen before include "Person who's smashing" , "Satellite aerial" , "broth?" , "course" , "What's presented on salver" .)