An improved partner in crime? (7)
I believe the answer is:
abetter
'partner in crime?' is the definition.
(I've seen this before)
'an improved' is the wordplay.
'an' becomes 'a'.
'improved' becomes 'better' (similar in meaning).
'a'+'better'='ABETTER'
(Other definitions for abetter that I've seen before include "associate" , "one who helps in a crime" , "He criminally assists" , "I'll help!" , "He helps criminal" .)