Praise for a cook is not rare (4,4)
I believe the answer is:
well done
'praise' is the definition.
I don't know anything about this answer so I cannot tell whether this works.
'cook is not rare' is the wordplay.
'cook' becomes 'well' (I am not sure about this - if you are sure you should believe this answer much more).
'is not rare' becomes 'done' (I've seen this in another clue).
'well'+'done'='WELL-DONE'
'for a' is the link.
Can you help me to learn more?
(Other definitions for well done that I've seen before include "By no means rare" , "How one might like one's steak?" , "Commendation for achievement" , "Far from rare" , "Congratulations - cooked right through" .)