An overdue converted try (9)
I believe the answer is:
endeavour
'try' is the definition.
(I know that try can be written as endeavour)
'an overdue converted' is the wordplay.
'converted' is an anagram indicator.
'an'+'overdue'='anoverdue'
'anoverdue' anagrammed gives 'ENDEAVOUR'.
(Other definitions for endeavour that I've seen before include "Aim" , "Morse" , "Captain Cook's first ship - DCI Morse's first name" , "Determined effort" , "First space shuttle to visit the International Space Station" .)