Wise men taking a long time on Sunday (5)
I believe the answer is:
sages
'wise men' is the definition.
(I've seen this before)
'a long time on sunday' is the wordplay.
'a long time' becomes 'ages' (ages can mean a very long time).
'on' is a charade indicator (letters next to each other).
'sunday' becomes 's'.
'ages' after 's' is 'SAGES'.
'taking' acts as a link.
(Other definitions for sages that I've seen before include "plants" , "Wise men" , "Learned people" , "enlightened people" , "Wise people" .)