My dog's nose wiggles (8)
I believe the answer is:
goodness
'my' is the definition.
(I've seen this before)
'dog's nose wiggles' is the wordplay.
'wiggles' is an anagram indicator (I've seen 'wiggle' mean this).
'dogs'+'nose'='dogsnose'
'dogsnose' is an anagram of 'GOODNESS'.
(Other definitions for goodness that I've seen before include "merit" , "Quality of being morally good or virtuous" , "Moral excellence" , "Virtue, righteousness" , "Virtue; excellence" .)