That's how pie ceremony reveals a fine specimen (9)
I believe the answer is:
Here is my best explanation:
'a fine specimen' is the definition.
'that's how pie ceremony reveals' is the wordplay.
'reveals' indicates a hidden word.
'SHOWPIECE' is hidden within 'thats how pie ceremony'.
(Other definitions for showpiece that I've seen before include "good example", "shining example", "Item for exhibition", "jewel", "especially fine example", "Fine example", "Very fine specimen", "fine specimen of its kind", "flagship" and "Item of work presented for display".)