Fewer round mammal (3)
I believe the answer is:
ewe
'round mammal' is the definition.
The answer and definition can be both animals as well as being singular nouns.
Maybe there's an association between them I don't understand?
'fewer' is the wordplay.
'EWE' is hidden in amongst the letters.
But, I am uncertain how this is indicated.
Can you help me to learn more?
(Other definitions for ewe that I've seen before include "One needing pastoral care" , "21a [SHEEP]" , "A palindromic sheep" , "Lamb's dam" , "Partner to ram" .)