Some percherons, of course, will eat fish (5)
I believe the answer is:
heron
'eat fish' is the definition.
I can't tell whether this definition defines the answer.
'some percherons of course' is the wordplay.
'some' indicates the answer is hidden within the clue (some parts of the word are used).
'HERON' can be found hidden inside 'percherons course'.
'will' is the link.
Can you help me to learn more?
(Other definitions for heron that I've seen before include "Wader" , "Large British wading bird" , "One bird" , "Graceful grey bird with long neck" , "Rhone (anag) - bird" .)