Eat away like characters in "Sweet Charity" (4)
I believe the answer is:
etch
'eat away' is the definition.
(I've seen this before)
'characters in sweet charity' is the wordplay.
'characters in' says the answer is hidden in the clue.
'ETCH' can be found hidden inside 'sweet charity'.
'like' acts as a link.
(Other definitions for etch that I've seen before include "Carve into surface, impress deeply" , "Inscribe" , "Engrave (metal/glass)" , "Mark" , "Carve into metal with acid" .)