A mountain of sugar, maybe, used in baked item? (4)
I believe the answer is:
loaf
'a mountain of sugar' is the definition.
'loaf' can be an answer for 'sugar' (loaf sugar is a kind of sugar). I'm not sure about the 'a mountain of' bit.
I don't understand the rest of the clue.
Can you help me to learn more?
(Other definitions for loaf that I've seen before include "Head (slang) -- be a slacker" , "Spend time idly, having slangy head" , "Head - bread" , "Bum about" , "Half of one is better than none" .)