Irish men taking car in ship for unprecedented events (6)

'unprecedented events' is the definition.
The definition and answer can be both acts as well as being plural nouns.
Maybe there's a link between them I don't understand?

'irish men taking car in ship' is the wordplay.
'irish men' becomes 'fir' (I am not sure about this - if you are sure you should believe this answer much more).
'taking' is a charade indicator (letters next to each other).
'car' becomes 't'.
'in' means one lot of letters goes inside another.
'ship' becomes 'ss'.
't' placed into 'ss' is 'sts'.
'fir'+'sts'='FIRSTS'

'for' is the link.

Can you help me to learn more?