Best ever log (6)
I believe the answer is:
record
This clue might be a double definition.
'best' is the first definition.
(similar in meaning)
'ever log' is the second definition.
'record' can be an answer for 'log' (I've seen this before). I'm not certain of the 'ever' bit.
Can you help me to learn more?
(Other definitions for record that I've seen before include "Log - so far unsurpassed" , "Chronicle or log" , "Document preserving information" , "Set down in permanent form" , "Note, register" .)