A bit of heat that her mum revealed (5)
I believe the answer is:
therm
'a bit of heat that her mum revealed' is the definition.
The definition and answer can be both quantities as well as being singular nouns.
Perhaps there's an association between them I don't understand?
'a bit of heat that her mum' is the wordplay.
'a bit of' indicates the answer is hidden within the clue.
'THERM' is hidden within 'heat that her mum'.
Can you help me to learn more?
(Other definitions for therm that I've seen before include "Unit of heat used in the UK as the basis of gas bills" , "A hot unit" , "it measures heat" , "Unit of heat energy" , "Former gas supply unit" .)