Insulting a strong nominal leader in government (10)

I believe the answer is:

affronting

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'insulting' is the definition.
('affront' can be a synonym of 'insult')

'a strong nominal leader in government' is the wordplay.
'strong' becomes 'f' (musical symbol for 'forte', 'strong' in Italian).
'nominal leader' becomes 'front' (I can't explain this - if you can you should give a lot more credence to this answer).
'government' becomes 'g' (abbreviation for government).
'a'+'f'+'front'+'in'+'g'='AFFRONTING'

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(Another definition for affronting that I've seen is " vexing".)

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

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