Pop a question that's somewhat obscure (6)
I believe the answer is:
opaque
'obscure' is the definition.
(I've seen this before)
'pop a question that's somewhat' is the wordplay.
'that's somewhat' says the answer is hidden in the clue.
'OPAQUE' can be found hidden inside 'pop a question'.
(Other definitions for opaque that I've seen before include "Not translucent" , "Impervious to light - hard to understand" , "Impenetrable to light" , "Not clearly expressed" , "Puzzling - dull" .)