Top cow (6)
I believe the answer is:
jersey
This might be a double definition.
'top' is the first definition.
(item of clothing)
'cow' is the second definition.
The definition and answer can be both animals as well as being singular nouns.
Maybe there's a link between them I don't understand?
Can you help me to learn more?
(Other definitions for jersey that I've seen before include "Channel land < top" , "Milked" , "Knitted garment" , "Warm garment or Channel Island" , "farm animal" .)