Throws in diamonds as forms of sales talk (7)

'throws' is the definition.
(pitch is a kind of throw)

'diamonds as forms of sales talk' is the wordplay.
I cannot really understand how this works, but
'sales talk' could be 'pitch' (synonyms) and 'pitch' is present in the answer.
The remaining letters 'es' is a valid word which might be clued in a way I don't see.
This may be the basis of the clue (or it may be nonsense).

'in' is the link.

Can you help me to learn more?