Part of the whole (7)
'part of the whole' is the definition.
('segment' is part of 'whole')
This is the entire clue.
(Other definitions for segment that I've seen before include "Part of a circle cut off by a chord" , "Part of citrus fruit" , "Part separable from other parts, say of orange" , "Division" , "Separate" .)
'part of the whole' is the definition.
('portion' is part of 'whole')
This is all the clue.
(Other definitions for portion that I've seen before include "allotment" , "Serving" , "Share, helping" , "A lot of" , "Piece of a whole" .)