What might jumping into nettles be — and cause? (4)
I believe the answer is:
rash
'cause?' is the definition.
Although both the answer and definition are singular nouns, I cannot understand how one could define the other.
I cannot understand how the rest of the clue works.
(Other definitions for rash that I've seen before include "Hasty; skin disorder" , "Skin redness" , "Foolish; skin problem" , "Eruption of spots on skin" , "Hotheaded" .)