I say, Edward, that's sharp! (5)
I believe the answer is:
honed
'sharp' is the definition.
(I've seen this in another clue)
'i say edward' is the wordplay.
'i say' becomes 'hon' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'edward' becomes 'Ed' (short for Edward).
'hon'+'ed'='HONED'
'that's' acts as a link.
Can you help me to learn more?
(Other definitions for honed that I've seen before include "Perfected" , "Refined" , "Sharpened with a stone" .)