Clue: Instruction to reader left English grad in charge of 16 scientist (9)
Answer: PTOLEMAIC
Explanation: Definition: of 16 scientist

**PTO** (please turn over, so "instruction to reader") + **L** (left) + **E** (English) + **MA** (Master of Arts, so "grad") + **IC** (in charge)
 
*Ptolemy (c100-c170) was an Egyptian polymath, so the 16 in the clue refers to the solution to 16d (EGYPTIAN)