Eve is upset by this riddle (5)
I believe the answer is:
sieve
'this riddle' is the definition.
(I've seen this before)
'eve is upset' is the wordplay.
'upset' says the letters should be written backwards.
'eve'+'is'='eveis'
'eveis' written backwards gives 'SIEVE'.
'by' is the link.
(Other definitions for sieve that I've seen before include "Meshed kitchen utensil" , "Fine riddle" , "Separate" , "Mesh used for straining or sifting" , "Straining device" .)