Dragon is ridiculously slow, for one (4,4)
I believe the answer is:
road sign
'slow for one' is the definition.
('SLOW' is an example of a road sign)
'dragon is ridiculously' is the wordplay.
'ridiculously' is an anagram indicator.
'dragon'+'is'='dragonis'
'dragonis' with letters rearranged gives 'ROAD SIGN'.
(Other definitions for road sign that I've seen before include "Bearer of warning" , "something that can be seen along the way" , "Roundabout ahead or T-junction, say" , "'It informs or instructs highway users (4,4)'" , "Notice for drivers" .)