Fiend, say, hogging start of road show (11)
I believe the answer is:
demonstrate
'show' is the definition.
('demonstrate' can be a synonym of 'show')
'fiend say hogging start of road' is the wordplay.
'fiend' becomes 'demon' (I've seen this before).
'say' becomes 'state' ('state' can be a synonym of 'say'**).
'hogging' indicates putting letters inside.
'start of' indicates taking the first letters.
The first letter of 'road' is 'r'.
'state' placed around 'r' is 'strate'.
'demon'+'strate'='DEMONSTRATE'
(Other definitions for demonstrate that I've seen before include "March" , "Make a public protest" , "Prove - protest" , "English floozies returning, led by villainous character" , "Prove, show" .)