Forever and always, including time with tiny changes (8)
I believe the answer is:
eternity
'forever' is the definition.
(synonyms)
'always including time with tiny changes' is the wordplay.
'always' becomes 'eer' (poetic way of saying ever).
'including' is an insertion indicator.
'time' becomes 't' (abbreviation).
'with' is a charade indicator (letters next to each other).
'changes' indicates anagramming the letters.
'eer' going around 't' is 'eter'.
'tiny' is an anagram of 'nity'.
'eter'+'nity'='ETERNITY'
'and' is the link.
(Other definitions for eternity that I've seen before include "Infinity" , "Ages and ages" , "That's a very long time" , "I try teen (anag.)" , "Age" .)