Reckoning on time, as it turned out (10)
I believe the answer is:
estimation
'reckoning' is the definition.
(estimation is a kind of reckoning)
'on time as it turned out' is the wordplay.
'turned out' indicates anagramming the letters.
'on'+'time'+'as'+'it'='ontimeasit'
'ontimeasit' is an anagram of 'ESTIMATION'.
(Other definitions for estimation that I've seen before include "Judgment" , "View" , "Guess" , "Opinion" , "Reckoning of value" .)