Half a dozen (3)
I believe the answer is:
six
'half a dozen' is the definition.
(I know that half a dozen can be written as six)
This is all the clue.
(Other definitions for six that I've seen before include "Maximum cricket hit" , "Number of bowls in a cricket over" , "larger boundary" , "VI" , "Knock for . . . - surprise or defeat" .)