Heads on the floor? What's up? (5)
I believe the answer is:
tails
'floor? what's up?' is the definition.
I can't judge whether this definition defines the answer.
'heads on the' is the wordplay.
'heads' becomes 'ails' (I can't explain this - if you can you should give a lot more credence to this answer).
'on' is a charade indicator (letters next to each other).
'the' becomes 't' (the is pronounced as a 't' sound in some dialects).
'ails' put after 't' is 'TAILS'.
Can you help me to learn more?
(Other definitions for tails that I've seen before include "the back of bears - bulls too" , "Follows closely" , "Animals' extremities" , "Gambler's choice" , "Coin-tossing call" .)