Whisper main number of forty-five? (5)
I believe the answer is:
aside
'whisper' is the definition.
I cannot understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for aside that I've seen before include "Apart; incidental remark" , "Separately" , "Remark by an actor, directly to audience say" , "Whispered comment" , "In reserve; actor's remark to audience" .)