An attempt in the past (3)

I believe the answer is:

ago

'in the past' is the definition.
(three years ago means three years in the past)

'an attempt' is the wordplay.
'an' becomes 'a'.
'attempt' becomes 'go' (go is a kind of attempt).
'a'+'go'='AGO'

(Other definitions for ago that I've seen before include "Back (in time)" , "Previously" , "In past times" , "Time past" , "Gone, past, since" .)

I've seen this clue in The Telegraph, The Globe and Mail and The Irish Independent.

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