Love is almost completely true and certain after time (8)
I believe the answer is:
treasure
'love' is the definition.
(both are terms of endearment)
'true and certain after time' is the wordplay.
'true' becomes 'rea' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'and' is a charade indicator (letters next to each other).
'certain' becomes 'sure' (synonyms).
'after' says to put letters next to each other.
'time' becomes 't' (abbreviation).
'rea' put next to 'sure' is 'reasure'.
'reasure' after 't' is 'TREASURE'.
'is almost completely' acts as a link.
I am not very happy about this link. Some or all of it may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for treasure that I've seen before include "Hold dear, prize" , "Valued possession, buried perhaps" , "Valuable hoard" , "Quantity of precious objects" , "someone valued" .)