In which to succeed, possibly as knights? (5)
I believe the answer is:
order
'in which to succeed possibly as knights?' is the definition.
Although both the answer and definition are singular nouns, I don't see how they can define each other.
This is the entire clue.
Can you help me to learn more?
(Other definitions for order that I've seen before include "Rank" , "Command harmony" , "eg OBE" , "an answer to all clues, initially" , "Tidy and settled condition" .)