Six-nil for a time? That’s bad! (7)
I believe the answer is:
violent
'bad' is the definition.
Both the answer and definition are adjectives. Perhaps you can see an association between them that I don't see?
'six-nil for a time?' is the wordplay.
'six' becomes 'vi' ('vi' can be a synonym of 'six').
'nil' becomes 'o'.
'for' means one lot of letters go next to another.
'a time?' becomes 'lent' (I have seen 'Time of fasting ' mean 'lent' so perhaps 'time' could also mean 'lent'**).
'vi'+'o'+'lent'='VIOLENT'
'that's' is the link.
Can you help me to learn more?
(Other definitions for violent that I've seen before include "Bloody" , "Sharp" , "Strong - destructive" , "Extreme(ly aggressive)" , "Using much force" .)