A Brontë's inside small volume (3)
I believe the answer is:
mil
'small volume' is the definition.
The definition and answer can be both quantities as well as being singular nouns.
Maybe you can see an association between them that I don't see?
'a bronte's inside' is the wordplay.
'a bronte' becomes 'emily' (I've seen this in another clue).
'inside' means to look at the middle letters.
The centre of 'emily' is 'MIL'.
Can you help me to learn more?
(Other definitions for mil that I've seen before include "One / one thousand inch" , "One thousandth of an inch" , "tiny distance" , "One thousanth of an inch" .)