Unwilling to bend, seeing a second fix on a London building succeeded (2,4,2,5)

'fix on a london building succeeded' is the definition.
I don't know anything about this answer so I cannot tell whether this works.

'unwilling to bend seeing a second' is the wordplay.
I cannot really understand how this works, but
'a' is within the answer.
'second' could be 's' (common abbreviation) and 's' is present in the answer.
'unwilling to bend' could be 'hardasnails' (hard-as-nails means stubborn or tough) and 'hardasnails' is found in the answer.
No letters remain.
This may be the basis of the clue (or it may be nonsense).

Can you help me to learn more?