Surprisingly similar to initial, invalid court proceeding (8)
I believe the answer is:
mistrial
'invalid court proceeding' is the definition.
'mistrial' can be an answer for 'proceeding' (mistrial is a kind of proceeding). I'm unsure of the 'invalid court' bit.
'surprisingly similar to initial' is the wordplay.
'surprisingly' is an anagram indicator (a surprising ordering of the letters).
'initial' suggests taking the first letters.
The initial letter of 'to' is 't'.
'similar'+'t'='similart'
'similart' with letters rearranged gives 'MISTRIAL'.
Can you help me to learn more?
(Other definitions for mistrial that I've seen before include "Court hearing invalidated by error" , "Defective hearing" , "Botched case in court" , "Inconclusive or invalid court proceedings" , "legal process going wrong" .)