Bad luck? It won't spread (4,6)
I believe the answer is:
hard cheese
'bad luck?' is the definition.
(I've seen this before)
'won't spread' is the wordplay.
'won't' becomes 'hard' (I can't explain this - if you can you should believe this answer much more).
'spread' becomes 'cheese spread' (cheese spread is a kind of spread).
'hard'+'cheese'='HARD CHEESE'
'it' acts as a link.
This may not be correct. It may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for hard cheese that I've seen before include "Expression of sympathy" , "Pecorino" , "Bad luck! (Grate it!)" , "Leicester" , "commiserating words" .)