Delighted to detect, you say (4)
I believe the answer is:
sent
'delighted' is the definition.
Although both the answer and definition are past participle verbs, I can't see how they can define each other.
I don't understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for sent that I've seen before include "old money in Tallinn" , "Noiseless" , "Shipped" , "Remitted" , "Told to go - enthralled" .)