Absolutely determined that Man will be proven innocent ultimately (4-4)
I believe the answer is:
hell-bent
'absolutely determined' is the definition.
(I've seen this before)
'man will be proven innocent ultimately' is the wordplay.
'man will' becomes 'he'll' ('he'll', contraction of 'he will').
'ultimately' indicates one should take the final letters.
The final letters of 'proven innocent' are 'nt'.
'hell'+'be'+'nt'='HELL-BENT'
'that' is the link.
(Other definitions for hell-bent that I've seen before include "Dogged - persistent" , "Determined at all costs" , "Recklessly determined" , "on path with good intentions" , "Absolutely determined" .)