One partial to fish, Ruth having no starter (5)
I believe the answer is:
egret
'one' is the definition.
Although both the answer and definition are singular nouns, I cannot understand how they can define each other.
I can't explain the rest of the clue.
Can you help me to learn more?
(Other definitions for egret that I've seen before include "Mainly white heron" , "Wader with white plumage" , "Kind of heron with long white feathers" , "young bird" , "Stork-like bird" .)