One's allotted portion (6)
I believe the answer is:
ration
'one's allotted portion' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for ration that I've seen before include "Restrict the supply of" , "Dole out portion due to shortage" , "Fixed restricted allowance" , "Restricted share" , "Share of food, etc" .)