It diverts wild herd going astray (3,7)
I believe the answer is:
red herring
'it diverts' is the definition.
The definition suggests a singular noun which matches the answer.
'wild herd going astray' is the wordplay.
'wild' indicates anagramming the letters.
'going astray' becomes 'erring' (err can mean to go the wrong way).
'herd' with letters rearranged gives 'redh'.
'redh'+'erring'='RED HERRING'
Can you help me to learn more?
(Other definitions for red herring that I've seen before include "bait, of a certain sort" , "Diversion intended to distract attention from the main issue" , "What distracts" , "Distraction" , "fish" .)