Practise endlessly producing tries again (7)
I believe the answer is:
rehears
'tries again' is the definition.
('hears' can be a synonym for 'tries' so perhaps 'rehears' is OK for 'tries again')
'practise endlessly' is the wordplay.
'practise' becomes 'rehearse' ('rehearse' can be a synonym of 'practise').
'endlessly' means to remove the last letter.
'rehearse' with its final letter taken away is 'REHEARS'.
'producing' is the link.
(Other definitions for rehears that I've seen before include "judges over" , "Once again tries" .)