Most absurd to get poorly during a short nap (8)
I believe the answer is:
silliest
'most absurd' is the definition.
(silly can mean absurd or foolish)
'poorly during a short nap' is the wordplay.
'poorly' becomes 'ill' (similar in meaning).
'during' is an insertion indicator.
'a short' means to remove the last letter.
'nap' becomes 'siesta' (siesta is a kind of nap).
'siesta' with its last letter removed is 'siest'.
'ill' placed within 'siest' is 'SILLIEST'.
'to get' is the link.
(Other definitions for silliest that I've seen before include "It's Ellis (anag)" , "Being least sensible" , "Most inane" , "Most ridiculous" , "Most stupid" .)