Mean to insist being on time (7)
I believe the answer is:
average
'mean' is the definition.
(I know that mean can be written as average)
'insist being on time' is the wordplay.
'insist' becomes 'aver' (I've seen this in another clue).
'being on' says to put letters next to each other.
'time' becomes 'age' (an age is a period of time).
'aver'+'age'='AVERAGE'
'to' acts as a link.
(Other definitions for average that I've seen before include "Normal in arithmetic way" , "Mean - ordinary" , "Mean, so-so" , "Mean, median or middling" , "just like any other" .)