Experts caught in dreadful congestion (11)
I believe the answer is:
cognoscenti
'experts' is the definition.
(I've seen this before)
'caught in dreadful congestion' is the wordplay.
'caught' becomes 'c' (cricket abbreviation).
'in' indicates putting letters inside.
'dreadful' is an anagram indicator.
'congestion' with letters rearranged gives 'cognosenti'.
'c' going within 'cognosenti' is 'COGNOSCENTI'.
(Other definitions for cognoscenti that I've seen before include "Those well-informed on a particular subject" , "Knowledgeable types" , "discerning experts?" , "Informed experts" , "Sophisticates" .)