Found duke leaving to get hold of new cloak (7)
I believe the answer is:
envelop
'cloak' is the definition.
(thesaurus)
I can't explain the rest of the clue.
Can you help me to learn more?
(Other definitions for envelop that I've seen before include "Give all-round cover" , "Shroud, cover up" , "Wrap up, cover on all sides" , "Enfold, enwrap" , "Compass" .)