Raised lumps in bedding (5)
I believe the answer is:
straw
'bedding' is the definition.
Although both the answer and definition are singular nouns, I cannot see how they can define each other.
'raised lumps' is the wordplay.
'raised' shows that the letters should be reversed in order (going up in a down clue).
'lumps' becomes 'warts' (I have seen 'unwanted lumps' mean 'warts' so perhaps 'lumps' could also mean 'warts').
'warts' back-to-front is 'STRAW'.
'in' acts as a link.
Can you help me to learn more?
(Other definitions for straw that I've seen before include "Stalk - tube for drinking" , "Pale yellow colour" , "trifle" , "corny stuff" , "Dry stalk of grain" .)