Follow orders (4)
(Other definitions for obey that I've seen before include "Follow orders" , "Respect" , "Conform" , "Toe the line" , "Accept instructions" .)
'follow orders' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for heed that I've seen before include "Careful attention" , "Caution" , "Observe" , "Obey" , "Take account of" .)