Some cocksure talk retracted in future (5)
I believe the answer is:
later
'in future' is the definition.
(I've seen this before)
'some cocksure talk retracted' is the wordplay.
'some' indicates a hidden word (some parts of the word are used).
'retracted' says the letters should be written backwards.
'retal' can be found hidden inside 'cocksure talk'.
'retal' written backwards gives 'LATER'.
(Other definitions for later that I've seen before include "When to see you?" , "at a future date" , "succeeding" , "there's more behind" , "Alert (anag.)" .)