Promising little ensign uses props incorrectly (15)

I believe the answer is:

unprepossessing

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'promising little' is the definition.
Both the definition and answer are adjectives. Perhaps there's a link between them I don't understand?

'ensign uses props incorrectly' is the wordplay.
'incorrectly' is an anagram indicator (I've seen this in other clues).
'ensign'+'uses'+'props'='ensignusesprops'
'ensignusesprops' is an anagram of 'UNPREPOSSESSING'.

Can you help me to learn more?

(Other definitions for unprepossessing that I've seen before include "Not appealing to the eye" , "off-putting" .)

I've seen this clue in The Daily Express.

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