Speak about renovation of dome in the future, perhaps? (7)
I believe the answer is:
someday
'in the future perhaps?' is the definition.
'speak about renovation of dome' is the wordplay.
'speak' becomes 'say' (I've seen this in other clues).
'about' means one lot of letters goes inside another.
'renovation of' indicates anagramming the letters (I've seen this in other clues).
'dome' with letters rearranged gives 'omed'.
'say' going around 'omed' is 'SOMEDAY'.
(Other definitions for someday that I've seen before include "At a future time; samoyed (anag.)" , "song" , "An unspecified time in the future" , "eventually" , "When will my prince come" .)