It's said to cause a smile, mostly eating last of pork chops (6)
I believe the answer is:
cheeks
'chops' is the definition.
(chops can mean your cheeks)
'it's said to cause a smile mostly eating last of pork' is the wordplay.
'it's said to cause a smile' becomes 'cheese' ('cheese' is said to make someone smile).
'mostly' means to remove the last letter.
'eating' is an insertion indicator.
'last of' indicates one should take the final letters.
The final letter of 'pork' is 'k'.
'cheese' with its final letter taken away is 'chees'.
'chees' going around 'k' is 'CHEEKS'.
(Other definitions for cheeks that I've seen before include "Addresses with impudence, using both sides of face" , "They're either side of the face" .)