Most remarkable trial absorbs everyone (7)
I believe the answer is:
tallest
'most remarkable' is the definition.
('tall' can mean surprising or unbelievable)
'trial absorbs everyone' is the wordplay.
'trial' becomes 'test' (synonyms).
'absorbs' is an insertion indicator.
'everyone' becomes 'all' (I've seen this before).
'test' going around 'all' is 'TALLEST'.
(Other definitions for tallest that I've seen before include "Sell tat (anag.)" , "highest standing" , "Of greatest height" , "Most lofty" , "Of extreme height" .)