Mysterious mixture of meat and icing (9)
I believe the answer is:
enigmatic
'mysterious' is the definition.
(I've seen this before)
'mixture of meat and icing' is the wordplay.
'mixture of' indicates an anagram (I've seen this in other clues).
'and' is a charade indicator (letters next to each other).
'meat' put after 'icing' is 'icingmeat'.
'icingmeat' is an anagram of 'ENIGMATIC'.
(Other definitions for enigmatic that I've seen before include "Obscure, puzzling" , "not obvious" , "with a mystery ingredient" , "Difficult to interpret" , "Puzzling, like the Sphinx" .)