Clue: Perhaps like 18's attractiveness and like 12? (6)
Answer: SATINY
Explanation: Definition: Perhaps like 18
***S**ex **A**ppeal="attractiveness"; plus **TINY**=like SMALLS – Edit thanks to Andrew*
 ~~the **S** from "18′**s**"; plus the head or "ness" of **A**ttractive/ness; plus **TINY**=like SMALLS~~