Sergeant out to part friends (8)
I believe the answer is:
estrange
'part friends' is the definition.
'estrange' can be an answer for 'part' (thesaurus). I am not certain of the 'friends' bit.
'sergeant out' is the wordplay.
'out' indicates anagramming the letters (out can mean wrong or inaccurate).
'sergeant' with letters rearranged gives 'ESTRANGE'.
'to' is the link.
Can you help me to learn more?
(Other definitions for estrange that I've seen before include "Divorce" , "Cause to become unfriendly using reagents" , "Get on the wrong side of" , "Ten gears (anag.)" , "Make enemy of sergeant" .)