"First off . . ." (3)
I believe the answer is:
one
(Other definitions for one that I've seen before include "Individual" , "Single, sole" , "Sole; number" , "Ace" , "Sole; identical" .)
I believe the answer is:
one
(Other definitions for one that I've seen before include "Individual" , "Single, sole" , "Sole; number" , "Ace" , "Sole; identical" .)