Against including cream to make soup extra (7)
I believe the answer is:
crouton
'make soup extra' is the definition.
I don't know anything about this answer so I cannot judge whether this works.
'against including cream' is the wordplay.
'against' becomes 'con' (as in pros and cons, for and against).
'including' means one lot of letters goes inside another.
'cream' becomes 'rout' (I've seen this in another clue).
'con' enclosing 'rout' is 'CROUTON'.
'to' is the link.
Can you help me to learn more?
(Other definitions for crouton that I've seen before include "lands in the soup" , "One's in the soup" , "little bit of bread" , "Fried garnish for soup" , "One might be in the soup" .)