Bagging 50, ace cricket side runs round quickly (7)

I believe the answer is:

allegro

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'quickly' is the definition.
(I've seen this in another clue)

'bagging 50 ace cricket side runs round' is the wordplay.
'bagging' is an insertion indicator (bag can mean to obtain or contain).
'50' becomes 'l' (Roman numeral).
'ace' becomes 'a' (abbreviation).
'cricket side' becomes 'leg' (I've seen this before).
'runs round' becomes 'ro' (I can't explain this - if you can you should give a lot more credence to this answer).
'a'+'leg'='aleg'
'l' going inside 'aleg' is 'alleg'.
'alleg'+'ro'='ALLEGRO'

Can you help me to learn more?

(Other definitions for allegro that I've seen before include "Quick (of a score)" , "Old car" , "Brisk and lively tempo, musically" , "Brisk musical piece" , "Scored at a brisk speed" .)

I've seen this clue in The Times.

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