Seemingly serious about late snooze, retires (7)

I believe the answer is:
deadpan
'seemingly serious' is the definition.
I can't tell whether this defines the answer.
'late snooze retires' is the wordplay.
'late' becomes 'dead' (similar in meaning).
'snooze' becomes 'nap' (synonyms).
'retires' says the letters should be written backwards.
'nap' reversed gives 'pan'.
'dead'+'pan'='DEADPAN'
'about' acts as a link.
Can you help me to learn more?
(Other definitions for deadpan that I've seen before include "Impassive" , "showing no emotion" , "Lifeless" , "Keeping a straight face" , "Poker-faced" .)
