Blight on the plant? This needs fencing (10)
I believe the answer is:
pentathlon
'this needs fencing' is the definition.
The definition suggests a singular noun which matches the answer.
'blight on the plant?' is the wordplay.
'blight' indicates anagramming the letters (I've seen 'blighted' mean this (I've seen this in other clues)).
'on'+'the'+'plant'='ontheplant'
'ontheplant' with letters rearranged gives 'PENTATHLON'.
Can you help me to learn more?
(Other definitions for pentathlon that I've seen before include "old Olympic event" , "Event of five different disciplines" , "athletic contest" , "Fivefold athletic event" , "Sporting event with five disciplines" .)