Baffler (5)
I believe the answer is:
poser
'baffler' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for poser that I've seen before include "Puzzling question for the model" , "Conundrum - model?" , "Difficult problem" , "Attitudiniser" , "Question - a sitter" .)