Was prostrate in narrative poem (3)
I believe the answer is:
lay
'narrative poem' is the definition.
(I've seen this before)
I don't understand the remainder of the clue.
Can you help me to learn more?
(Other definitions for lay that I've seen before include "Impose (a burden)" , "gamble" , "like a minister? On the contrary" , "Put down; lyric" , "Place (bet)" .)