Bonito shark eating rubbish (4)
I believe the answer is:
tosh
'rubbish' is the definition.
(I've seen this before)
'bonito shark eating' is the wordplay.
'eating' indicates the answer is hidden within the clue.
'TOSH' is hidden in the letters of 'bonito shark'.
(Other definitions for tosh that I've seen before include "Hooey" , "Baloney, twaddle" , "Nonsense (colloq.)" , "Nonsense; shot (anag.)" , "13 [TRIPE]" .)