Officer briefly backing the best legend (7)

I believe the answer is:

caption

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'legend' is the definition.
(synonyms)

'officer briefly backing the best' is the wordplay.
'officer briefly' becomes 'capt' (I am not sure about the 'briefly' bit.).
'backing' says the letters should be written backwards.
'the best' becomes 'noi' (resembles No. c, the best).
'noi' back-to-front is 'ion'.
'capt'+'ion'='CAPTION'

Can you help me to learn more?

(Other definitions for caption that I've seen before include "Legend with a photograph" , "Explanation of an illustration" , "Explanatory words or heading" , "Elegance of dress" , "Provide (a picture) with a title" .)

I've seen this clue in The Times.

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