One cooking in jacket, tricky problem (3,6)
I believe the answer is:
hot potato
I believe this is a double definition.
'one cooking in jacket' is the first definition.
(as in a jacket potato)
'tricky problem' is the second definition.
(I've seen this before)
(Other definitions for hot potato that I've seen before include "Awkward or delicate situation" , "contentious question" , "Situation likely to cause trouble, like thermal spud" , "controversial political issue?" , "tricky case" .)