Commonplace argument for state in command (7)

I believe the answer is:

prosaic

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'commonplace' is the definition.
(synonyms)

'argument for state in command' is the wordplay.
'argument' becomes 'pro' (pro is a kind of argument).
'for state' becomes 'sa' (I am not sure about this - if you are sure you should believe this answer much more).
'in command' becomes 'ic' (military abbreviation).
'pro'+'sa'+'ic'='PROSAIC'

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(Other definitions for prosaic that I've seen before include "Pedestrian, unimaginative" , "Workaday" , "Unimaginative - air cops (anag)" , "Lacking wit or imagination, dull" , "Lacking originality" .)

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

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