Fiery sailor with zeal to reform (6)
I believe the answer is:
ablaze
'fiery' is the definition.
(I've seen this before)
'sailor with zeal to reform' is the wordplay.
'sailor' becomes 'ab' (abbreviation for able seaman).
'with' is a charade indicator (letters next to each other).
'to reform' indicates an anagram (letters in a new form).
'zeal' anagrammed gives 'laze'.
'ab'+'laze'='ABLAZE'
(Other definitions for ablaze that I've seen before include "Flaming; on fire" , "burnt" , "Fiery" , "being toasted?" , "Well-lit" .)