Little fish thoroughly sautéed — it's first for gut-busting cuisine (3-3)
I believe the answer is:
fry-ups
'gut-busting cuisine' is the definition.
(unhealthy breakfasts)
'little fish thoroughly sauteed it's first' is the wordplay.
'little fish' becomes 'fry' (I've seen this in another clue).
'thoroughly' becomes 'up' ('up' can mean 'thoroughly' in some contexts).
'it's first' says to take the initial letters.
The first letter of 'sauteed' is 's'.
'fry'+'up'+'s'='FRY-UPS'
'for' acts as a link.
(Other definitions for fry-ups that I've seen before include "Dishes cooked in oil" , "Big breakfasts!" .)