Many a racecourse is considered lucky by the superstitious (6)
I believe the answer is:
mascot
'considered lucky by the superstitious' is the definition.
I know that 'lucky' relates to this answer.
'many a racecourse' is the wordplay.
'many' becomes 'M' (Roman numeral for a thousand).
'a racecourse' becomes 'ascot' (British racecourse).
'm'+'ascot'='MASCOT'
'is' acts as a link.
Can you help me to learn more?
(Other definitions for mascot that I've seen before include "Something considered to bring good luck" , "Lucky charm" , "Good luck token" , "Symbolic figure, of a team perhaps" , "good luck charm required" .)