Flowers came up on Sunday (5)
I believe the answer is:
roses
'flowers' is the definition.
(rose is a type of flower)
'came up on sunday' is the wordplay.
'came up' becomes 'Rose' (I've seen this before).
'on' says to put letters next to each other.
'sunday' becomes 's'.
'rose'+'s'='ROSES'
(Other definitions for roses that I've seen before include "the wars" , "Flowers for watering cans?" , "Occupants of bed" , "northern counties, symbolically" , "Ramblers, for example" .)