Untrue statement about roughage (5)
I believe the answer is:
fibre
'roughage' is the definition.
(I've seen this before)
'untrue statement about' is the wordplay.
'untrue statement' becomes 'fib' (fib is a kind of statement. I am not sure about the 'untrue' bit.).
'about' becomes 're' ('re' means regarding or about).
'fib'+'re'='FIBRE'
Can you help me to learn more?
(Other definitions for fibre that I've seen before include "Thread, filament" , "Basis of yarn" , "Texture - strength of character" , "Thread, strand" , "(Material composed of) thread(s)" .)