Poem in Hesiod execrable (3)
I believe the answer is:
ode
'poem' is the definition.
(I know that ode is a type of poem)
'in hesiod execrable' is the wordplay.
'in' indicates the answer is hidden within the clue.
'ODE' can be found hidden inside 'hesiod execrable'.
(Other definitions for ode that I've seen before include "(Railway)system" , "A poem celebrating person or event" , "Poem in praise of doe" , "Literary work" , "- - to a 12 Urn" .)