Saintly gatekeeper's famous rabbit (5)
I believe the answer is:
'rabbit' is the definition.
(I've seen this in another clue)
I cannot understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for peter that I've seen before include "One of Jesus' disciples", "Blue -, ship's flag", "Boy's name (maybe blue)", "Leader of the Apostles", "- Grimes (Britten)".)