Application that's ultimately fantastic on paper? (5)
I believe the answer is:
cream
'application' is the definition.
The definition and answer can be both man-made objects as well as being singular nouns.
Perhaps you can see an association between them that I can't see?
'ultimately fantastic on paper?' is the wordplay.
'ultimately' indicates one should take the final letters.
'on' is a charade indicator (letters next to each other) (in a down clue, letters appear on others).
'paper?' becomes 'ream' (a ream is an amount of paper).
The final letter of 'fantastic' is 'c'.
'c'+'ream'='CREAM'
'that's' is the link.
Can you help me to learn more?
(Other definitions for cream that I've seen before include "Milk product" , "Dairy product" , "Best - ointment" , "Top or best part" , "Top of milk or society" .)