Sharp tooth, end rough (2,3,3)
I believe the answer is:
on the dot
'sharp' is the definition.
(both can mean promptly)
'tooth end rough' is the wordplay.
'rough' is an anagram indicator (a rough or broken ordering of the letters).
'tooth'+'end'='toothend'
'toothend' anagrammed gives 'ON THE DOT'.
(Other definitions for on the dot that I've seen before include "Promptly" , "at exactly the arranged time" , "At precisely the right time" , "At exactly the right time" , "Absolutely punctual" .)