An expression of congratulation to a smart individual (4,3)
I believe the answer is:
nice one
'an expression of congratulation' is the definition.
I don't know anything about this answer so I can't judge whether it can be defined by this definition.
'smart individual' is the wordplay.
'smart' becomes 'nice' (I can't explain this - if you can you should give a lot more credence to this answer).
'individual' becomes 'one' (an individual is one person).
'nice'+'one'='NICE ONE'
'to a' acts as a link.
Can you help me to learn more?
(Other definitions for nice one that I've seen before include "like it!" , "Congratulatory phrase" , "very good" .)