Old Charlie in employment allowed to leave (7)
I believe the answer is:
excused
'allowed to leave' is the definition.
I can't tell whether this defines the answer.
'old charlie in employment' is the wordplay.
'old' becomes 'ex' (prefix meaning former or onetime).
'charlie' becomes 'c' (phonetic alphabet: alpha, bravo, charlie etc.).
'in employment' becomes 'used' (I can't justify this - if you can you should give a lot more credence to this answer).
'ex'+'c'+'used'='EXCUSED'
Can you help me to learn more?
(Other definitions for excused that I've seen before include "Forgiven" , "Given permission to leave, or pardoned" , "Exempted from task" , "Overlooked offence or released from duty" , "Exonerated" .)