Bread portion (4)
(Other definitions for loaf that I've seen before include "Some bread; 10 (slang)" , "more than just crumbs!" , "Mass of bread" , "Head - bread" , "bloomer, say" .)
'bread portion' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for slice that I've seen before include "shot in golf that goes astray" , "poor golf shot" , "Helping (of cake, roast meat)" , "Portion (of cake)" , "Piece cut from a larger portion" .)