Record 50% of ambulances needing overhaul (5)

I believe the answer is:

album

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'record' is the definition.
(I've seen this in another clue)

I don't understand the rest of the clue.

(Other definitions for album that I've seen before include "Book for displaying a collection" , "Item of music released" , "place for photos" , "series of tracks" , "Blank book for mounting photos, stamps etc" .)

I've seen this clue in The Irish Times.

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