A little bit of soup's being warmed up for the audience (7)
I believe the answer is:
soupcon
'a little' is the definition.
(a soupcon is a small amount of something)
'bit of soup's being warmed up for the audience' is the wordplay.
I cannot quite understand how this works, but
'bit' could be 'sou' (I have seen 'A bit' mean 'sou' so perhaps 'bit' could also mean 'sou') and 'sou' is present in the answer.
'of' could be 'o' and 'o' is found within the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for soupcon that I've seen before include "Tiny quantity" , "A very small quantity, from French" , "very little" , "Small amount of food" , "A vary small quantity, just a trace - from France" .)