Fix us some dessert (6)
I believe the answer is:
mousse
'dessert' is the definition.
(I know that mousse is a type of dessert)
'fix us some' is the wordplay.
'fix' is an anagram indicator.
'us'+'some'='ussome'
'ussome' anagrammed gives 'MOUSSE'.
(Other definitions for mousse that I've seen before include "cold dish" , "Light creamy dessert, set with gelatin" , "A hair dressing; a creamy sweet" , "Whipped savoury dish" , "Foamy dish" .)