Difference between a request and an order (6)
I believe the answer is:
please
'difference between' is the definition.
I can't tell whether this definition defines the answer.
'a request and an order' is the wordplay.
'a request' becomes 'plea' (plea is a kind of request).
'and' is a charade indicator (letters next to each other).
'an order' becomes 'se' (I can't justify this - if you can you should give a lot more credence to this answer).
'plea'+'se'='PLEASE'
Can you help me to learn more?
(Other definitions for please that I've seen before include "if you don't mind" , "Want" , "Delight; amuse" , "Asleep (anag)" , "If you'd be so kind?" .)