Assert time is typical (7)
I believe the answer is:
average
'typical' is the definition.
(I've seen this in another clue)
'assert time' is the wordplay.
'assert' becomes 'aver' (averring is a kind of asserting).
'time' becomes 'age' (an age is a period of time).
'aver'+'age'='AVERAGE'
'is' is the link.
(Other definitions for average that I've seen before include "Mean, so-so" , "Mean - norm" , "The statistical norm" , "building society customer loses capital over time" , "Medial" .)