Dreadful in operation, ignoring a command (9)
I believe the answer is:
directive
'command' is the definition.
(directive is a kind of command)
'dreadful in operation ignoring a' is the wordplay.
'dreadful' becomes 'dire' ('dire' can be a synonym of 'dreadful').
'in operation' becomes 'active' (I've seen this before).
'ignoring' is a deletion indicator.
'active' with 'a' taken out is 'ctive'.
'dire'+'ctive'='DIRECTIVE'
(Other definitions for directive that I've seen before include "Official instruction" , "command" , "order" .)