Clarify about penalty (6)
I believe the answer is:
refine
'clarify' is the definition.
(thesaurus)
'about penalty' is the wordplay.
'about' becomes 're' (regarding).
'penalty' becomes 'fine' (fine is a kind of penalty).
're'+'fine'='REFINE'
(Other definitions for refine that I've seen before include "Purify or improve" , "Cleanse from impurities" , "Purify or make more cultured" , "Hone" , "Make purer" .)