Part sentimental English left out (10)
I believe the answer is:
instalment
'part' is the definition.
(I have seen 'part of serial' mean 'instalment' so perhaps 'part' could also mean 'instalment')
'sentimental english left out' is the wordplay.
'english' becomes 'e' (abbreviation).
'left' indicates named letters should be taken away.
'out' indicates anagramming the letters (out can mean wrong or inaccurate).
'sentimental' with 'e' taken away is 'sntimental'.
'sntimental' with letters rearranged gives 'INSTALMENT'.
(Other definitions for instalment that I've seen before include "Payment of part of debt" , "Chapter" , "episode" , "part of serial" , "One of a series of partial payments" .)