JFK co-star, reformed man of low degree? (4,5)
I believe the answer is:
jack frost
'man of low degree?' is the definition.
(as in low degrees of temperature)
'jfk co-star reformed' is the wordplay.
'reformed' indicates an anagram.
'jfk'+'co'+'star'='jfkcostar'
'jfkcostar' anagrammed gives 'JACK FROST'.
(Other definitions for jack frost that I've seen before include "Cold weather, personified" , "Personification of freezing weather" , "Freezing weather personified" , "Personification of a wintry morning" , "nipper" .)