Rude bum in novel is lying (9)
I believe the answer is:
recumbent
'is lying' is the definition.
(I've seen this before)
'rude bum in novel' is the wordplay.
'rude' is an anagram indicator.
'in' is an insertion indicator.
'novel' becomes 'recent' (both can mean new).
'bum' is an anagram of 'umb'.
'umb' going inside 'recent' is 'RECUMBENT'.
(Other definitions for recumbent that I've seen before include "flat?" , "Lying down comfortably" .)