Who knows when protests arising, indeed (7)
I believe the answer is:
someday
'who knows' is the definition.
I can't judge whether this definition defines the answer.
'protests arising indeed' is the wordplay.
'protests' becomes 'demos' (demonstrations).
'arising' says the letters should be written backwards.
'indeed' becomes 'ay' ('ay' and 'aye' can mean yes).
'demos' back-to-front is 'somed'.
'somed'+'ay'='SOMEDAY'
'when' is the link.
Can you help me to learn more?
(Other definitions for someday that I've seen before include "eventually" , "At a future time; samoyed (anag.)" , "song" , "An unspecified time in the future" , "When will my prince come" .)