### Clue: Plain idle and amorous, lifting top of nightie (13)
### Answer: MONOCHROMATIC 
 ### Explanation: Definition: Plain
 MOOCH(to idle;to loiter around) + ROMANTIC(amorous) **with the 1st letter of**(top of) "nightie " **moved up**(lifting …, in a down clue).
Defn: …, literally, of one colour.