Perfect declaration of one distributing cards (5)
I believe the answer is:
ideal
'perfect declaration' is the definition.
'ideal' can be an answer for 'perfect' (I've seen this before). I am not sure about the 'declaration' bit.
'one distributing cards' is the wordplay.
'one' becomes 'i' (Roman numeral).
'distributing cards' becomes 'deal' (I am not sure about this - if you are sure you should believe this answer much more).
'i'+'deal'='IDEAL'
'of' is the link.
(Other definitions for ideal that I've seen before include "Very eager (to see)" , "Paragon" , "Perfect; a standard of perfection" , "Textbook" , "Optimal" .)