Additional text ratified in part (5)
I believe the answer is:
extra
'additional' is the definition.
(extra means additional or surplus)
'text ratified in part' is the wordplay.
'in part' says the answer is hidden in the clue.
'EXTRA' is hidden within 'text ratified'.
(Other definitions for extra that I've seen before include "wide? It could be" , "Ancillary" , "Not a hit certainly" , "Supplemental" , "Run scored but not off the bat" .)