Denial about still mostly being in a bad way (7)
I believe the answer is:
nastily
'denial about still mostly being in a bad way' is the definition.
I can't judge whether this definition defines the answer.
'denial about still mostly' is the wordplay.
'denial' becomes 'nay' (nay is a kind of denial).
'about' means one lot of letters goes inside another.
'mostly' means to remove the last letter (most but not all of the word).
'still' with its last letter removed is 'stil'.
'nay' enclosing 'stil' is 'NASTILY'.
Can you help me to learn more?
(Other definitions for nastily that I've seen before include "In an unpleasant manner" , "Such is the threatening way" , "Unpleasantly" , "in a horrid way" .)