Helping reserve to create means for allocating scarce resources (6,4)

I believe the answer is:

ration book

'means for allocating scarce resources' is the definition.
(book for allocating rations)

'helping reserve' is the wordplay.
'helping' becomes 'ration' (a ration is a serving or helping).
'reserve' becomes 'book' (to book something is to reserve it).
'ration'+'book'='RATION-BOOK'

'to create' is the link.

I've seen this clue in The Guardian.

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