Something lucky in mother's bed (6)
I believe the answer is:
mascot
'something lucky' is the definition.
(I know that mascot are lucky)
'mother's bed' is the wordplay.
'mother's' becomes 'ma's' (Ma is another word for mother or mum).
'bed' becomes 'cot' (cot is a type of bed).
'mas'+'cot'='MASCOT'
'in' is the link.
(Other definitions for mascot that I've seen before include "Team's good luck bringer" , "Symbolic figure, of a team perhaps" , "Does it get you first place" , "Bringer of good luck to team, etc" , "Lucky charm" .)