Where to jot down manoeuvres by military reserve (8,4)

I believe the answer is:

exercise book

'where to jot down' is the definition.

'manoeuvres by military reserve' is the wordplay.
'manoeuvres by military' becomes 'exercise'.
'reserve' becomes 'book' (booking is a kind of reserving).
'exercise'+'book'='EXERCISE BOOK'

(Another definition for exercise book that I've seen is " School item".)

I've seen this clue in The Times.

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