Not getting a mite worried about it? Never! (2,2,4)
I believe the answer is:
at no time
'never' is the definition.
(synonyms)
'not getting a mite worried about it?' is the wordplay.
'getting' means one lot of letters go next to another.
'worried' is an anagram indicator (worry can mean to interfere with or disturb).
'about it?' is an insertion indicator (some letters go around or about others).
'a' put after 'mite' is 'mitea'.
'mitea' anagrammed gives 'atime'.
'not' going inside 'atime' is 'AT NO TIME'.
(Another definition for at no time that I've seen is " Never".)