I'm in business to make a speech (6)
I believe the answer is:
tirade
'a speech' is the definition.
(I know that tirade is a type of declamation)
'i'm in business' is the wordplay.
'i'm' becomes 'i' (I've seen this in other clues).
'in' is an insertion indicator.
'business' becomes 'trade' (trade is a kind of business).
'i' placed within 'trade' is 'TIRADE'.
'to make' acts as a link.
(Other definitions for tirade that I've seen before include "Inclination; fish" , "Verbal outburst" , "Long speech of angry criticism" , "Long angry piece of denunciation" , "Vocal abuse" .)