Botched expression that could bring poet harm? (5,8)
I believe the answer is:
mixed metaphor
'harm?' is the definition.
Both the answer and definition are singular nouns.
Perhaps you can see a link between them that I can't see?
I can't explain the rest of the clue.
(Other definitions for mixed metaphor that I've seen before include "Ridiculous combination of two figures of speech" , "Incongruous combination of descriptive figures of speech" , "literary blunder" , ""A rolling stone is worth two in the bush", for example" , "This tower of strength will forge ahead, for instance" .)