Most suspenseful points witnessed in the trial (7)
I believe the answer is:
tensest
'most suspenseful' is the definition.
('tense' can be similar in meaning to 'suspenseful')
'points witnessed in the trial' is the wordplay.
'points' becomes 'Ns' (N is an example).
'witnessed' becomes 'e' (I am not sure about this - if you are sure you should believe this answer much more).
'in the' indicates putting letters inside.
'trial' becomes 'test' (synonyms).
'ns'+'e'='nse'
'nse' placed inside 'test' is 'TENSEST'.
Can you help me to learn more?
(Other definitions for tensest that I've seen before include "Most tightly stretched" , "Most strained" , "Most stressed" , "Most up-tight" .)