Coin has the middle part raised (4)
I believe the answer is:
dime
'coin' is the definition.
(I know that dime is a type of coin)
'has the middle part raised' is the wordplay.
'part' indicates the answer is hidden within the clue.
'raised' shows that the letters should be reversed in order (going up in a down clue).
'emid' is hidden in the letters of 'has the middle'.
'emid' in reverse letter order is 'DIME'.
(Other definitions for dime that I've seen before include "10 US cents" , "Something round and silvery" , "Ten cents in USA" , "Two nickels" , "Ten-cent piece" .)