Tricky question for model (5)
I believe the answer is:
poser
This clue is a double definition.
'tricky question' is the first definition.
(I've seen this in another clue)
'model' is the second definition.
(synonyms)
'for' is the link.
(Other definitions for poser that I've seen before include "subject for an artist?" , "Maybe model" , "Pseud" , "Ropes (anag.)" , "Attitudiniser" .)