### Clue: Inscrutable type — he's quiet during lean times (3,6)
### Answer: THE SPHINX 
 ### Explanation: Definition: Inscrutable type
 { [ HE'S + P(abbrev. for "piano", musical direction to play softly;quietly) ] **contained in**(during) THIN(lean;unsubstantial) } + X(symbol for multiplication in arithmetic;times).
Answer: From Egyptian mythology where sphinxes gave people puzzles to solve, and thus were considered mysterious and inscrutable.