It isn’t legal till I return to arrest in-charge (7)
I believe the answer is:
illicit
'it isn't legal' is the definition.
The definition suggests a singular noun but the answer is not.
'till i return to arrest in-charge' is the wordplay.
'return' is a reversal indicator.
'to arrest' is an insertion indicator.
'in charge' becomes 'ic' (abbreviation for 'in charge').
'till'+'i'='tilli'
'tilli' back-to-front is 'illit'.
'illit' enclosing 'ic' is 'ILLICIT'.
Can you help me to learn more?
(Other definitions for illicit that I've seen before include "Forbidden by law, rules" , "Not legal" , "not conforming to regulations" , "wrong" , "breaking the rules" .)