Attempt again (5)
I believe the answer is:
retry
'attempt again' is the definition.
('try' can be a synonym for 'attempt' so perhaps 'retry' is OK for 'attempt again')
This is the entire clue.
(Other definitions for retry that I've seen before include "Make a further attempt" , "Advice following failure, initially" , "Put on trial again" , "take second opinion on case" , "Have another go" .)