The bit of tart and ice, I left (5)
I believe the answer is:
piece
'the bit of' is the definition.
(I've seen this before)
'tart and ice i left' is the wordplay.
'tart' becomes 'pie' (I've seen this in other clues).
'and' means one lot of letters go next to another.
'left' indicates named letters should be taken away (some letters have left).
'ice' with 'i' taken out is 'ce'.
'pie'+'ce'='PIECE'
(Other definitions for piece that I've seen before include "man on board" , "Single article" , "constituent" , "artefact" , "Musical work; bit" .)