Rate found on fish (5)
I believe the answer is:
scale
This clue could be a double definition.
'rate' is the first definition.
(thesaurus)
'on fish' is the second definition.
The answer and definition can be both animals as well as being singular nouns.
I also know that 'fish' relates to this answer.
'found' is the link.
Can you help me to learn more?
(Other definitions for scale that I've seen before include "Hierarchy" , "Deposit formed in a kettle or on teeth" , "An ordered series of units for measurement purposes" , "Group of notes in ascending or descending order" , "Alec's (anag) -- graduation" .)