Speaks in support of European party and explains (10)

'explains' is the definition.
The definition and answer can be both to do with communicating as well as being verbs in their -s form.
Maybe there's a link between them I don't understand?

'speaks in support of european party' is the wordplay.
'speaks' becomes 'orates' (orating is a kind of speaking).
'in support of' means one lot of letters go next to another (in a down clue, some letters hold others up).
'european' becomes 'E' (abbreviation e.g. EU).
'party' becomes 'lab' (abbreviation for Labour).
'e'+'lab'='elab'
'orates' after 'elab' is 'ELABORATES'.

'and' acts as a link.

Can you help me to learn more?