Clue: He's really missed the combination of today's themes (9)
Answer: ARAUCARIA
Explanation: He's really missed the combination of today's themes (9)
**ARAUCARIA** (aka Rev John Galbraith Graham), a former crossword compiler, who would have been 100 today, and who is "really missed". 
 
 
*Today's themes are MONKEYs and PUZZLEs and any fan of the great man will know that ARAUCARIA is the Latin name for the MONKEYPUZZLE tree.