Opportunity to chain one escapee to castle walls (6)
I believe the answer is:
chance
'opportunity' is the definition.
(I know that opportunity can be written as chance)
'chain one escapee to castle walls' is the wordplay.
I cannot really see how this works, but
'chain' could be 'ch' (abbreviation for the unit of length) and 'ch' is present in the answer.
'one' could be 'an' (an apple is one apple) and 'an' is located in the answer.
This may be the basis of the clue (or it may be nonsense).
'to' is the link.
Can you help me to learn more?
(Other definitions for chance that I've seen before include "Accidental - try" , "he unpredictable element of life" , "Risk the opportunity" , "Luck or accident" , "Lady luck" .)