Opportunist, almost the last character to appear in court (8)
I believe the answer is:
chancery
'court' is the definition.
(type of court)
'opportunist almost the last character to appear' is the wordplay.
'opportunist' becomes 'chancer' (someone taking chances).
'almost' means to remove the last letter (most of the word but not all of it).
'the last' indicates one should take the final letters.
'to appear' becomes 'y' (I can't explain this - if you can you should believe this answer much more).
The final letter of 'character' is 'r'.
'chancer' with its final letter taken away is 'chance'.
'chance'+'r'+'y'='CHANCERY'
'in' is the link.
Can you help me to learn more?
(Other definitions for chancery that I've seen before include "Where Jarndyce suit languished" , "Public record office" , "He can cry (anag.)" , "Lord Chancellor's court" , "Court of public archives" .)