Partners take one day in Rome (5)
I believe the answer is:
nones
'day in rome' is the definition.
(I've seen this before)
'partners take one' is the wordplay.
'partners' becomes 'ns' (North and South are partners in the game bridge).
'take' means one lot of letters goes inside another.
'ns' placed around 'one' is 'NONES'.
(Other definitions for nones that I've seen before include "Roman monthly date" , "Church service held at the 9th hour" , "Day in Roman calendar, nine days before ides" , "day in ancient Rome" , "Time to pray" .)