Portion, part (5)
I believe the answer is:
piece
I believe this is a double definition.
'portion' is the first definition.
(I know that piece is a type of portion)
'part' is the second definition.
(I know that part can be written as piece)
(Other definitions for piece that I've seen before include "Firearm -- collector's item" , "Artwork" , "King, perhaps" , "Single article" , "Slice" .)