Information from guard at Alcatraz (4)

I believe the answer is:

data

'information' is the definition.
(data are bits of information)

'from guard at alcatraz' is the wordplay.
'from' says the answer is hidden in the clue.
'DATA' can be found hidden inside 'guard at alcatraz'.

(Other definitions for data that I've seen before include "Gathered stats" , "Collected information" , "Facts and figures as fed to computers (4)" , "Input; facts" , "Facts - Star Trek android" .)

I've seen this clue in The Sun.

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