Some Wrens ignore US officer (6)

I believe the answer is:

ensign

'us officer' is the definition.
(rank in some US armed forces)

'some wrens ignore' is the wordplay.
'some' says the answer is hidden in the clue (some of the parts of the word are used).
'ENSIGN' is hidden within 'wrens ignore'.

(Other definitions for ensign that I've seen before include "Flag - junior American naval officer" , "Military or naval flag" , "SECOND PART OF 10" , "Flag; standard-bearer" , "Ship's colours" .)

I've seen this clue in The Telegraph.

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