Order pie, virtually packed with stuff, kilo sent back (5,5)
I believe the answer is:
quick march
'order' is the definition.
(I've seen this before)
'pie virtually packed with stuff kilo sent back' is the wordplay.
'pie virtually' becomes 'quich' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'packed with' means one lot of letters goes inside another.
'stuff' becomes 'cram' (cramming is a kind of stuffing).
'kilo' becomes 'k' (phonetic alphabet: alpha, bravo, charlie etc.).
'sent back' says the letters should be written backwards.
'cram'+'k'='cramk'
'cramk' in reverse letter order is 'kmarc'.
'quich' enclosing 'kmarc' is 'QUICK MARCH'.
Can you help me to learn more?
(Other definitions for quick march that I've seen before include "Military movement order (to foot soldiers?)" , "Military command (to step on it!)" , "Order for soldiers to move" , "may be part of a tattoo?" .)