In letting the herd stray around, cause obstruction (6)
I believe the answer is:
hinder
'in letting the' is the definition.
I can't judge whether this definition defines the answer.
'herd stray around cause obstruction' is the wordplay.
'stray' indicates an anagram.
'around' is an insertion indicator.
'cause obstruction' becomes 'in' (I can't justify this - if you can you should give a lot more credence to this answer).
'herd' anagrammed gives 'hder'.
'hder' going around 'in' is 'HINDER'.
Can you help me to learn more?
(Other definitions for hinder that I've seen before include "Obstruct; nearer the back" , "Handicap, impede" , "block" , "Obstruct, present an obstacle" , "Keep back by delaying progress" .)