Parts (of a whole) (5)
I believe the answer is:
units
'parts of a whole' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for units that I've seen before include "Single parts of a whole" , "Individual things as parts of a whole" , "Apparatus similar to barbecue" , "Detachments" , "Single things" .)