Lister re-used point that's clean (7)
I believe the answer is:
sterile
'clean' is the definition.
(sterile can mean clean or disinfected)
'lister re-used point' is the wordplay.
I cannot quite understand how this works, but
an anagram of 'lister' is 'steril' which is within the answer.
'point' could be 'e' (compass point) and 'e' is found within the answer.
This accounts for all the letters.
This may be the basis of the clue (or it may be nonsense).
'that's' acts as a link.
Can you help me to learn more?
(Other definitions for sterile that I've seen before include "Free from living micro-organisms, absolutely clean" , "Not able to produce offspring" , "Not producing offspring" , "Uninspired" , "Aseptic or infertile" .)