Infected relative with a touch of norovirus (7)
I believe the answer is:
unclean
'infected' is the definition.
(I've seen this before)
'relative with a touch of norovirus' is the wordplay.
'relative' becomes 'uncle' (uncle is a kind of relative**).
'with' is a charade indicator (letters next to each other).
'touch of' indicates taking the first letters.
The initial letter of 'norovirus' is 'n'.
'uncle'+'a'+'n'='UNCLEAN'
(Other definitions for unclean that I've seen before include "Defiled" , "Dirty; immoral" , "(Ritually) tainted" , "Dirty or unwashed" , "Ceremonially impure" .)