Command includes singular advice for the inept (6)
I believe the answer is:
resign
'advice for the inept' is the definition.
I can't tell whether this definition defines the answer.
'command includes singular' is the wordplay.
'command' becomes 'reign'.
'includes' indicates putting letters inside.
'singular' becomes 's' (abbreviation sometimes used in dictionaries).
'reign' going around 's' is 'RESIGN'.
Can you help me to learn more?
(Other definitions for resign that I've seen before include "advice for the incompetent?" , "surrender" , "Quit" , "admit defeat" , "Either leave" .)