### Clue: Bit on the side? Lock phone card up first (8)
### Answer: MISTRESS 
 ### Explanation: Definition: Bit on the side
 TRESS(a long lock of hair) **placed below**(… first, in a down clue) **reversal of**(… up, in a down clue) SIM(abbrev. for "subscriber identification module", the card in your mobile phone).