Relative raises cats and dogs in the nunnery (10)
I believe the answer is:
stepsister
'relative' is the definition.
(stepsister is a kind of relative)
I cannot understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for stepsister that I've seen before include "relative in law" , "member of the family" , "Relation gained through a second marriage" , "one who hated Cinderella" .)