Departing vagrant then outwardly in debt (2,3,4)
I believe the answer is:
on the wing
'departing' is the definition.
The definition and answer are not the same part of speech.
'vagrant then outwardly in debt' is the wordplay.
'vagrant' indicates anagramming the letters (I've seen this in other clues).
'outwardly' means one lot of letters goes inside another (some letters go outside others).
'in debt' becomes 'owing' (I've seen this before).
'then' is an anagram of 'nthe'.
'nthe' inserted into 'owing' is 'ON THE WING'.
Can you help me to learn more?
(Other definitions for on the wing that I've seen before include "down the touchline" , "Where feathers are" , "flier" , "Where one used to see 7 or 11" , "in the air" .)