One looking a bit ratty, but capable of love (4)
I believe the answer is:
vole
'one looking a bit ratty but capable' is the definition.
Although both the answer and definition are singular nouns, I cannot see how they can define each other.
'of love' is the wordplay.
'of' indicates anagramming the letters (the answer comes from or 'of' the letters).
'love' with letters rearranged gives 'VOLE'.
Can you help me to learn more?
(Other definitions for vole that I've seen before include "Strange love for a rodent" , "Small mouse-like rodent" , "Love for a small burrowing mammal" , "Love this rodent, strangely" , "win all the tricks" .)