Speaker swallows one drink as a starter (10)
I believe the answer is:
originator
'a starter' is the definition.
The definition and answer can be both people as well as being singular nouns.
Perhaps they are linked in a way I don't understand?
'speaker swallows one drink as' is the wordplay.
'speaker' becomes 'orator' (orator is a kind of speaker).
'swallows' is an insertion indicator.
'one drink as' becomes 'igin' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'orator' enclosing 'igin' is 'ORIGINATOR'.
Can you help me to learn more?
(Other definitions for originator that I've seen before include "Father" , "founder" , "Creator, initiator" .)