Translation of prose is a problem (5)
I believe the answer is:
poser
'is a problem' is the definition.
(I've seen this before)
'translation of prose' is the wordplay.
'translation of' is an anagram indicator (I've seen this in other clues).
'prose' with letters rearranged gives 'POSER'.
(Other definitions for poser that I've seen before include "One pretends to be something they are not" , "Question; one trying to impress" , "What's difficult" , "Brain-teaser" , "Sticky problem" .)