Cause of rash effects in bed? (7)
I believe the answer is:
nettles
'cause of rash effects in bed?' is the definition.
I can't tell whether this definition defines the answer.
'rash effects in bed?' is the wordplay.
'rash' becomes 'nettle rash' (nettle rash is a kind of rash).
'effects in bed?' becomes 's' (I can't justify this - if you can you should give a lot more credence to this answer).
'nettle'+'s'='NETTLES'
Can you help me to learn more?
(Other definitions for nettles that I've seen before include "One acting Chief Inspector on TV" , "Irritates" , "Plants with stinging hairs" .)