Mix in a dream sauce (8)
I believe the answer is:
marinade
'sauce' is the definition.
(I have seen 'spicy sauce' mean 'marinade' so perhaps 'sauce' could also mean 'marinade')
'mix in a dream' is the wordplay.
'mix' indicates anagramming the letters.
'in'+'a'+'dream'='inadream'
'inadream' with letters rearranged gives 'MARINADE'.
(Other definitions for marinade that I've seen before include "Mixture for soaking meat before cooking" , "get saturated" , "Spiced liquid in which food is soaked before cooking" , "Steep in seasoning" , "Mixture for soaking food before cooking" .)