Headless bugler grabbing one: what could be more hideous? (6)
I believe the answer is:
uglier
'more hideous?' is the definition.
('ugly' can be similar in meaning to 'hideous')
'headless bugler grabbing one' is the wordplay.
'headless' means to remove the first letter.
'grabbing' is an insertion indicator.
'one' becomes 'i' (roman numeral).
'bugler' with its first letter taken away is 'ugler'.
'ugler' placed around 'i' is 'UGLIER'.
'what could be' acts as a link.
(Other definitions for uglier that I've seen before include "More unpleasant to look at" , "More offensive to look at" , "Less pleasing to look at" , "Less appealing" , "Less beautiful" .)