Chance hamburger and omelette slice (6)
I believe the answer is:
random
'chance' is the definition.
(similar in meaning)
'hamburger and omelette slice' is the wordplay.
'slice' indicates the answer is hidden within the clue.
'RANDOM' is hidden in the letters of 'hamburger and omelette'.
(Other definitions for random that I've seen before include "Disorganised" , "Lacking any definite plan, order or purpose" , "unmethodical" , "Occurring by chance, no fixed pattern" , "Wild" .)