Mothers bed is a bringer of fortune (6)
I believe the answer is:
mascot
'bringer of fortune' is the definition.
The definition suggests a singular noun which matches the answer.
'mothers bed' is the wordplay.
'mothers' becomes 'mas' (ma is a kind of mother).
'bed' becomes 'cot' (cot is a type of bed).
'mas'+'cot'='MASCOT'
'is a' acts as a link.
Can you help me to learn more?
(Other definitions for mascot that I've seen before include "good luck charm required" , "Character or object used to bring good luck, or represent an organisation" , "It brings good luck" , "Does it get you first place" , "Something considered to bring good luck" .)