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 defines the answer.
'herd stray around cause obstruction' is the wordplay.
'stray' is an anagram indicator.
'around' means one lot of letters goes inside another.
'cause obstruction' becomes 'in' (I can't explain this - if you can you should believe this answer much more).
'herd' with letters rearranged gives 'hder'.
'hder' enclosing '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" .)