Difficult question from guy by river (6)
I believe the answer is:
teaser
'difficult question' is the definition.
(I've seen this before)
'guy by river' is the wordplay.
'guy' becomes 'tease' (I've seen this before).
'by' says to put letters next to each other.
'river' becomes 'r'.
'tease'+'r'='TEASER'
'from' acts as a link.
(Other definitions for teaser that I've seen before include "A difficult problem of Teresa" , "Riddle" , "Hard question" , "One who pulls someone's leg" , "Easter (anag) - puzzle" .)