Greedily eat course standing up (4)
I believe the answer is:
wolf
'greedily eat' is the definition.
'wolf' can be an answer for 'eat' (wolfing is a kind of eating). I am not certain of the 'greedily' bit.
'course standing up' is the wordplay.
'course' becomes 'flow' (synonyms).
'standing up' shows that the letters should be reversed in order (in a down clue up is reverse order).
'flow' written backwards gives 'WOLF'.
Can you help me to learn more?
(Other definitions for wolf that I've seen before include "Carnivore -- breed of 13 down" , "shovel down" , "Carnivorous pack animal" , "Pack hunter" , "gorge" .)