Easy for one in military intelligence having compromised Danish PM (10)
I believe the answer is:
midshipman
'easy for one' is the definition.
(I've seen this before)
'military intelligence having compromised danish pm' is the wordplay.
'military intelligence' becomes 'MI' (as in MI5 or MI6 - British military intelligence).
'having' is a charade indicator (letters next to each other).
'compromised' is an anagram indicator (I've seen 'compromising' mean this (compromise can mean change)).
'danish'+'pm'='danishpm'
'danishpm' anagrammed gives 'dshipman'.
'mi'+'dshipman'='MIDSHIPMAN'
'in' is the link.
(Other definitions for midshipman that I've seen before include "Easy for one" , "Sailor" , "Royal Navy rank" , "Probationary rank of young naval officer" , "Probationary naval officer's rank" .)