Instruction from dreadful court — a number beheaded (9)
I believe the answer is:
directive
'instruction' is the definition.
(I have seen 'Official instruction ' mean 'directive' so perhaps 'instruction' could also mean 'directive')
'dreadful court a number beheaded' is the wordplay.
'dreadful' becomes 'dire' (synonyms).
'court' becomes 'ct' (abbreviation used in road names).
'a number' becomes 'five' (five is a number).
'beheaded' means to remove the first letter (the head of the word is removed).
'five' with its first letter taken off is 'ive'.
'dire'+'ct'+'ive'='DIRECTIVE'
'from' is the link.
(Other definitions for directive that I've seen before include "order" , "Official instruction" , "command" .)