Proverbs nowadays take a long time (6)
I believe the answer is:
adages
'proverbs' is the definition.
('adage' can be a synonym of 'proverb')
'nowadays take a long time' is the wordplay.
'nowadays' becomes 'AD' (AD, Anno Domini, as opposed to BC, Before Christ).
'take' means one lot of letters go next to another.
'a long time' becomes 'ages' (ages can mean a very long time).
'ad'+'ages'='ADAGES'
(Other definitions for adages that I've seen before include "'Proverbs, saws (6)'" , "'Proverbs, true sayings (6)'" , "Wise old sayings" , "Old sayings, proverbs" , "Proverbs from sad age" .)