Past master's second attempt (3)
I believe the answer is:
ago
'past' is the definition.
(similar in meaning)
'master's second attempt' is the wordplay.
'master's second' becomes 'a' (2nd letter of 'master').
'attempt' becomes 'go' (go is a kind of attempt).
'a'+'go'='AGO'
(Other definitions for ago that I've seen before include "(Years) before the present time" , "Previously" , "Time past" , "Back (in time)" , "Gone, past, since" .)