Late start — very bad but not forbidden (6)
I believe the answer is:
lawful
'not forbidden' is the definition.
The answer and definition are different parts of speech. However, adjectives and past participle verbs can sometimes mean the same thing.
'late start very bad' is the wordplay.
'start' indicates taking the first letters.
'very bad' becomes 'awful' (I've seen this before).
The first letter of 'late' is 'l'.
'l'+'awful'='LAWFUL'
'but' is the link.
Can you help me to learn more?
(Other definitions for lawful that I've seen before include "Licit" , "Right!" , "Legal" , "Allowed" , "Legitimate" .)