Old Armory became head of local Government (4,5)

I believe the answer is:

lord mayor

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'head of local government' is the definition.
The definition suggests a singular noun which matches the answer.

'old armory became' is the wordplay.
'became' indicates an anagram (I've seen 'becoming' mean this).
'old'+'armory'='oldarmory'
'oldarmory' with letters rearranged gives 'LORD MAYOR'.

Can you help me to learn more?

(Other definitions for lord mayor that I've seen before include "VIP in London, perhaps" , "magistrate" , "head for city" , "elected as this?" , "Title of first citizen of a city" .)

I've seen this clue in the Sydney Morning Herald.

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