Occasional builder holding second job at bookies (9)

'job at bookies' is the definition.
I don't know anything about this answer so I cannot tell whether it can be defined by this definition.

'occasional builder holding second' is the wordplay.
'occasional' becomes 'odd' (odd can mean occasional or infrequent).
'builder' becomes 'maker' (I've seen this in another clue).
'holding' means one lot of letters goes inside another.
'second' becomes 's' (common abbreviation).
'odd'+'maker'='oddmaker'
'oddmaker' placed around 's' is 'ODDSMAKER'.

Can you help me to learn more?