Pastry containing meat from a real slug - so unusual! (7,4)
I believe the answer is:
sausage roll
'pastry' is the definition.
(I know that sausage roll is a type of pastry)
'a real slug so unusual' is the wordplay.
'unusual' indicates anagramming the letters.
'a'+'real'+'slug'+'so'='arealslugso'
'arealslugso' with letters rearranged gives 'SAUSAGE-ROLL'.
'containing meat from' is the link.
This may not be right. Some or all of it may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for sausage roll that I've seen before include "Baked meat product in pastry" , "Pork and pastry snack" , "Minced meat in pastry snack" , "Party fare" , "Party nibble" .)