Nothing grim that we might sense (5)
I believe the answer is:
odour
'that we might sense' is the definition.
(an odour can be sensed with smell)
'nothing grim' is the wordplay.
'nothing' becomes 'O' (looks like zero - 0).
'grim' becomes 'dour' (synonyms).
'o'+'dour'='ODOUR'
(Other definitions for odour that I've seen before include "Olfactory sensation" , "reputation" , "Aroma or fragrance" , "Smell; repute" , "Nasty smell" .)