Amazing card, exceptional, the tops! (3)
I believe the answer is:
ace
'tops' is the definition.
(synonyms)
I cannot understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for ace that I've seen before include "Tennis serve that the receiver can't reach" , "Very good; playing card" , "Possibly a diamond" , "Brilliant" , "Card with a single pip" .)