Possibly an overdue attempt (9)
I believe the answer is:
endeavour
'attempt' is the definition.
(I know that endeavour is a more specific form of the action attempt)
'possibly an overdue' is the wordplay.
'possibly' is an anagram indicator.
'an'+'overdue'='anoverdue'
'anoverdue' with letters rearranged gives 'ENDEAVOUR'.
(Other definitions for endeavour that I've seen before include "Determined effort" , "famous ship" , "Aspire; attempt" , "Strive - Inspector Morse's first name" , "Expenditure of effort" .)