Journalist supporting American politician is excited (5)

'excited' is the definition.
Both the definition and answer are past participle verbs.
Perhaps they are linked in a way I don't understand?

'journalist supporting american politician' is the wordplay.
'journalist' becomes 'ed' (short for editor).
'supporting' says to put letters next to each other (in a down clue, some letters go below others).
'american' becomes 'a' (common abbreviation - e.g. in organisation names).
'politician' becomes 'MP' (Member of Parliament).
'a'+'mp'='amp'
'ed' put after 'amp' is 'AMPED'.

'is' acts as a link.

Can you help me to learn more?