Times are changing by the second (4)
I believe the answer is:
eras
'times' is the definition.
(era is a kind of time)
'are changing by the second' is the wordplay.
'changing' indicates anagramming the letters.
'by' says to put letters next to each other.
'the second' becomes 's' (common abbreviation).
'are' is an anagram of 'era'.
'era'+'s'='ERAS'
(Other definitions for eras that I've seen before include "Periods, ages" , "Epochs" , "Periods of time" , "At least two times" , "typeface" .)