### Clue: Small amount of drink mopped up by a tissue, falsely? That's an understatement (7)
### Answer: LITOTES 
 ### Explanation: Definition: an understatement
An envelope ('mopped up by') of TOT ('small amount of drink') in LIES ('a tissue, falsely'. I take this as a reference to courtroom dramas in which a witness is accused of uttering "a tissue of lies").