Possible killer on board, clue so hot? (4,6)
I believe the answer is:
lead piping
'possible killer on board' is the definition.
I can't tell whether this definition defines the answer.
'clue so hot?' is the wordplay.
'clue' becomes 'lead' (I've seen this before).
'so hot?' becomes 'piping' (I can't justify this - if you can you should give a lot more credence to this answer).
'lead'+'piping'='LEAD PIPING'
Can you help me to learn more?
(Another definition for lead piping that I've seen is " Old Cluedo weapon".)