Left and right blocking various impediments to rapid progress? (1-7)

I believe the answer is:

l-drivers

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'impediments to rapid progress?' is the definition.
I don't know anything about this answer so I can't judge whether it can be defined by this definition.

'left and right blocking various' is the wordplay.
'left' becomes 'l' (common abbreviation).
'and' says to put letters next to each other.
'right' becomes 'r' (common abbreviation).
'blocking' means one lot of letters goes inside another.
'various' becomes 'divers' (I've seen this before).
'r' inserted within 'divers' is 'drivers'.
'l'+'drivers'='L-DRIVERS'

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I've seen this clue in The Independent.

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