Duke leaves MP to state main points again (5)
I believe the answer is:
recap
'state main points again' is the definition.
I can't tell whether this defines the answer.
'duke leaves mp' is the wordplay.
'duke' becomes 'd' (abbreviation).
'leaves' indicates named letters should be taken away.
'mp' becomes 'redcap' (Military Police officers are called redcaps).
'redcap' with 'd' taken away is 'RECAP'.
'to' is the link.
Can you help me to learn more?
(Other definitions for recap that I've seen before include "Reiterate" , "Sum up (abbrev.)" , "Run over the points again" , "Summary (abbr.)" , "Go over again; summarise" .)