Surprisingly porcine, old sheep's cheese (8)
I believe the answer is:
pecorino
'sheep's cheese' is the definition.
'pecorino' can be an answer for 'cheese' (I've seen this before). I also know that 'sheep' relates to this answer.
'surprisingly porcine old' is the wordplay.
'surprisingly' indicates an anagram.
'old' becomes 'o' (common abbreviation eg in OE for Old English).
'porcine' is an anagram of 'pecorin'.
'pecorin'+'o'='PECORINO'
(Other definitions for pecorino that I've seen before include "Hard cheese!" , "Italian cheese made from ewe's milk" , "Italian sheep's cheese" .)