Fruit consumed in Downing Street initially (5)
I believe the answer is:
dates
'fruit' is the definition.
(type of fruit)
'consumed in downing street initially' is the wordplay.
'consumed' becomes 'ate' (to eat is to consume food).
'in' indicates putting letters inside.
'initially' indicates taking the first letters.
The initial letters of 'downing street' is 'ds'.
'ate' inserted into 'ds' is 'DATES'.
(Other definitions for dates that I've seen before include "Small tree-fruits or social appointments" , "Sweet edible fruits of a palm" , "Fruits for social engagements" , "Fruits and pre-arranged meetings" , "Dried fruit" .)