Wild herd going astray and this could put you off the scent (3,7)
I believe the answer is:
red herring
'this could put you off the scent' is the definition.
The definition suggests a singular noun which matches the answer.
'wild herd going astray' is the wordplay.
'wild' indicates an anagram.
'going astray' becomes 'erring' (err can mean to go the wrong way).
'herd' anagrammed gives 'redh'.
'redh'+'erring'='RED HERRING'
'and' is the link.
Can you help me to learn more?
(Other definitions for red herring that I've seen before include "fish" , "An irrelevance" , "bait, of a certain sort" , "Cover" , "What distracts" .)