Speak about march returning sooner or later (7)
I believe the answer is:
someday
'sooner or later' is the definition.
Both the answer and definition are adverbs. Perhaps they are linked in a way I don't understand?
'speak about march returning' is the wordplay.
I cannot really understand how this works, but
'about' could be 'some' ('some' can be a synonym of 'about') and 'some' is located in the answer.
The remaining letters 'day' is a valid word which might be clued in a way I don't understand.
This may be the basis of clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for someday that I've seen before include "When will my prince come" , "eventually" , "song" , "An unspecified time in the future" , "At a future time; samoyed (anag.)" .)