Chewed on eastern snack (4)
I believe the answer is:
bite
'snack' is the definition.
(I know that snack can be written as bite)
'chewed on eastern' is the wordplay.
'chewed' becomes 'bit'.
'on' says to put letters next to each other (in a down clue, letters appear on others).
'eastern' becomes 'e'.
'bit'+'e'='BITE'
(Other definitions for bite that I've seen before include "The taking of bait by a fish" , "Pungency" , "Mouthful" , "(Of fish) take the bait" , "Get teeth into" .)