It won't lead someone astray to endorse picket
I believe the answer is:
signpost
'it won't lead someone astray' is the definition.
The definition suggests a singular noun which matches the answer.
'endorse picket' is the wordplay.
'endorse' becomes 'sign' (I've seen this before).
'picket' becomes 'post' (I've seen this before).
'sign'+'post'='SIGNPOST'
'to' is the link.
Can you help me to learn more?
(Other definitions for signpost that I've seen before include "One may help you on your way" , "It shows the way" , "this will give you directions" , "Waymark" , "director" .)