Investing round figure in boring club is a punt? (8)

'a punt?' is the definition.
Although both the answer and definition are singular nouns, I don't understand how one could define the other.

'investing round figure in boring club' is the wordplay.
'investing' means one lot of letters goes inside another (inserted letters are taken in or invested).
'round figure' becomes 'o'.
'in boring' becomes 'flat' (flat can mean dull or lifeless. I am not sure about the 'in' bit.).
'club' becomes 'bat' (as in sporting equipment).
'flat'+'bat'='flatbat'
'o' placed within 'flatbat' is 'FLATBOAT'.

'is' acts as a link.

Can you help me to learn more?