Left a clean plate at the dump, occasionally (3,2)
I believe the answer is:
ate up
'left a clean plate' is the definition.
'at the dump occasionally' is the wordplay.
'occasionally' means one should take alternating letters.
'at'+'the'+'dump'='atthedump'
The alternate letters of 'atthedump' are 'ATE UP'.
(Other definitions for ate up that I've seen before include "Squandered" , "preoccupied" , "Absorbed" .)