Yankee must follow imperial order and toe the line (4)
I believe the answer is:
obey
'toe the line' is the definition.
(I've seen this in another clue)
'yankee must follow imperial order' is the wordplay.
'yankee' becomes 'Y' (phonetic alphabet: alpha, bravo, charlie etc.).
'must follow' is a charade indicator (letters next to each other).
'imperial order' becomes 'obe' (Order of the British Empire award. I am not sure about the 'imperial' bit.).
'y' after 'obe' is 'OBEY'.
'and' is the link.
Can you help me to learn more?
(Other definitions for obey that I've seen before include "Submit to authority" , "Follow orders" , "Carry out (orders)" , "Do as one's told" , "Follow the instructions" .)