Second to none? Fourth-rate? That's a first! (8)
I believe the answer is:
premiere
'first' is the definition.
('premiere' can be similar in meaning to 'first')
'second to none? fourth-rate? that's a' is the wordplay.
I cannot really see how this works, but
'that's' could be 'ie' and 'ie' is found within the answer.
This may be the basis of clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for premiere that I've seen before include "First ever public performance" , "First screening" , "Play's first public performance" , "First showing of play or film" , "First show" .)