A long time to cry about a change of tune (7)
I believe the answer is:
century
'a long time' is the definition.
(I've seen this in another clue)
'cry about a change of tune' is the wordplay.
'about' means one lot of letters goes inside another.
'a change of' is an anagram indicator (the letter order is changed).
'tune' anagrammed gives 'entu'.
'cry' enclosing 'entu' is 'CENTURY'.
'to' is the link.
(Other definitions for century that I've seen before include "One hundred years" , "Group of a hundred" , "100 years" , "Period of time" , "lot of time" .)