Gray's said to eat leaves (5)
I believe the answer is:
graze
'eat leaves' is the definition.
(I've seen this before)
'gray's said' is the wordplay.
'said' shows a homophone (sound like).
'grays' is a homophone of 'GRAZE'.
'to' acts as a link.
(Other definitions for graze that I've seen before include "(Cow) feed; scrape" , "Browse; scratch" , "Tend at pasture" , "Feed in meadow" , "Scratch on skin" .)