Muriel, a bright little thing (5)
I believe the answer is:
spark
This clue could be a double definition.
'muriel' is the first definition.
Both the definition and answer are singular nouns.
Maybe they are linked in a way I don't understand?
'a bright little thing' is the second definition.
The definition and answer can be both human attributes as well as being singular nouns.
Perhaps there's an association between them I don't understand?
Can you help me to learn more?
(Other definitions for spark that I've seen before include "Particle of fire" , "Fiery particle" , "Quantity of electricity" , "Tiny, red-hot particle" , "Fragment of a burning substance" .)