Lance is broken, but not dirty (5)
I believe the answer is:
clean
'not dirty' is the definition.
('clean' is the opposite to 'dirty')
'lance is broken' is the wordplay.
'is broken' indicates an anagram.
'lance' with letters rearranged gives 'CLEAN'.
'but' is the link.
(Other definitions for clean that I've seen before include "Pure, hygienic" , "Not dirty" , "remove filth" , "Devoid of dirt" , "Free from dirt; well defined" .)