Holding the French in English court is brilliant success (5)
I believe the answer is:
'brilliant success' is the definition.
(I've seen this before)
'holding the french in english court' is the wordplay.
'holding' indicates putting letters inside.
'the french' becomes 'la'.
'in english' becomes 'e' (abbreviation. I am not sure about the 'in' bit.).
'court' becomes 'ct'.
'la' put into 'ect' is 'ECLAT'.
'is' is the link.
Can you help me to learn more?
(Other definitions for eclat that I've seen before include "Ostentation" , "Brilliance" , "Social distinction in France" , "Fame -- style" , "great success" .)