By way of example, they make firm declaration (13)
I believe the answer is:
pronouncement
'declaration' is the definition.
(pronouncement is a kind of declaration)
'by way of example they make firm' is the wordplay.
'by' is a charade indicator (letters next to each other).
'way of example they' becomes 'pronoun' (I can't explain this - if you can you should give a lot more credence to this answer).
'make firm' becomes 'cement' (I've seen this in another clue).
'pronoun' put next to 'cement' is 'PRONOUNCEMENT'.
Can you help me to learn more?
(Other definitions for pronouncement that I've seen before include "Edict" , "Official declaration" , "assertion" , "ordinance" , "official statement" .)