Clue: Absence of new tenant, back working earlier, observed at social event (13)
Answer: NONATTENDANCE
Explanation: Definition: Absence

[**back**] **<=ON** ("working") *earlier* than (i.e. before) ***(tenant)** [anag:*new*] *observed at* **DANCE** ("social event")
 
*Enumeration should have been (3-10).