Sweet food in steamer with a sour look about it (6)
I believe the answer is:
mousse
'sweet food' is the definition.
(type of dessert)
'steamer with a sour look about it' is the wordplay.
'steamer' becomes 'SS' (prefix in ship names eg SS Great Britain).
'with' is a charade indicator (letters next to each other).
'a sour look about' becomes 'mou' (I am not sure about this - if you are sure you should believe this answer much more).
'it' becomes 'e' ('e' can mean 'electronic' which is similar to 'IT').
'ss' after 'mou' is 'mouss'.
'mouss'+'e'='MOUSSE'
'in' is the link.
(Other definitions for mousse that I've seen before include "Pope's representative" , "cold dish" , "Fluffy pudding" , "Frothy, creamy dessert" , "Whipped sweet" .)