Attorney volunteers facts gathered for reference (4)

I believe the answer is:

data

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'facts gathered for reference' is the definition.
I can't tell whether this defines the answer.

'attorney volunteers' is the wordplay.
'attorney' becomes 'DA' (district attorney).
'volunteers' becomes 'TA' (abbreviation for Territorial Army).
'da'+'ta'='DATA'

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(Other definitions for data that I've seen before include "Numerical facts" , "Results of research" , "Organised information" , "Information for/from computer" , "Raw facts" .)

I've seen this clue in The Daily Express.

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