Fragments torn with one brief opening (5)

I believe the answer is:

intro

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'brief opening' is the definition.
'intro' can be an answer for 'opening' (I've seen this before). I am not sure about the 'brief' bit.

'fragments torn with one' is the wordplay.
'fragments' indicates an anagram.
'with' means one lot of letters goes inside another.
'one' becomes 'i' (Roman numeral**).
'torn' anagrammed gives 'ntro'.
'ntro' placed around 'i' is 'INTRO'.

Can you help me to learn more?

(Other definitions for intro that I've seen before include "Opening bars of a song" , "Nitro (anag.)" , "Early music piece" , "Launch" , "Beginning (informal)" .)

I've seen this clue in The Mirror.

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