Children behind vital part impair rapid progress (5,5)

I believe the answer is:

quick march

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'children behind vital part impair' is the definition.
I can't tell whether this defines the answer.

'rapid progress' is the wordplay.
'rapid' becomes 'quick' (synonyms).
'progress' becomes 'march' (march is a kind of progress).
'quick'+'march'='QUICK MARCH'

Can you help me to learn more?

(Other definitions for quick march that I've seen before include "Order for soldiers to move" , "Military command (to step on it!)" , "may be part of a tattoo?" , "Military movement order (to foot soldiers?)" .)

I've seen this clue in The Telegraph.

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