Initially on the loose without permission (4)
I believe the answer is:
awol
'permission' is the definition.
Although both the answer and definition are singular nouns, I cannot understand how they can define each other.
'initially on the loose without' is the wordplay.
'initially' suggests taking the first letters.
'the loose' becomes 'awl' (I am not sure about this - if you are sure you should believe this answer much more).
'without' is an insertion indicator.
The first letter of 'on' is 'o'.
'o' going within 'awl' is 'AWOL'.
Can you help me to learn more?
(Other definitions for awol that I've seen before include "Missing without permission" , "Of soldier, illegally absent - initially" , "Absent without leave (abbr.)" , "On the lam" , "Take unofficial leave (abbrev.)" .)