One dab (3)
I believe the answer is:
ace
I believe this clue is a double definition.
'one' is the first definition.
(ace has a value of one in some card games)
'dab' is the second definition.
(thesaurus)
(Other definitions for ace that I've seen before include "Outstanding" , "strained" , "Tennis winner" , "Expert; one" , "'wicked'!" .)