One who drives for leg breaks (6)
I believe the answer is:
golfer
'one who drives' is the definition.
The answer is a person as well as being a singular noun. This is suggested by the definition.
'for leg breaks' is the wordplay.
'breaks' is an anagram indicator.
'for'+'leg'='forleg'
'forleg' with letters rearranged gives 'GOLFER'.
Can you help me to learn more?
(Other definitions for golfer that I've seen before include "Player with clubs and tees" , "Driver, chipper and putter" , "Player on links" , "McGinley or Harrington, say" , "Swinger on course" .)