Modern coffee — recommended daily allowance unknown (6-3)
I believe the answer is:
latter-day
'modern' is the definition.
(I've seen this before)
'coffee recommended daily allowance unknown' is the wordplay.
'coffee' becomes 'latte' (type of coffee drink).
'recommended daily allowance' becomes 'rda' (this could be a standard abbreviation I've not previously seen).
'unknown' becomes 'y' (algebra).
'latte'+'rda'+'y'='LATTER-DAY'
Can you help me to learn more?
(Other definitions for latter-day that I've seen before include "Modern" , "Belonging to recent times" , "Church of Jesus Christ of ... Saints" , "Mormons belong to The Church of the . . . . . .-. . . Saints" , "Contemporary" .)