Fresh sandwiches are prepared with first of processed cheese (10)
I believe the answer is:
caerphilly
'cheese' is the definition.
(thesaurus)
'fresh sandwiches are prepared with first of processed' is the wordplay.
'fresh' becomes 'chilly' (I can't justify this - if you can you should give a lot more credence to this answer).
'sandwiches' is an insertion indicator (goes on either side like a sandwich).
'prepared with' indicates anagramming the letters.
'first of processed' becomes 'p' (cst letter of 'processed').
'are' anagrammed with 'p' can make 'aerp'.
'chilly' placed around 'aerp' is 'CAERPHILLY'.
Can you help me to learn more?
(Other definitions for caerphilly that I've seen before include "Mild white cheese" , "Welsh town" , "Town north of Cardiff" .)