Lieutenant, appearing about middle of film, has a pleasing accent (4)
I believe the answer is:
lilt
'a pleasing accent' is the definition.
'lilt' can be an answer for 'accent' (I have seen 'Gentle accent ' mean 'lilt' so perhaps 'accent' could also mean 'lilt'). I am not certain of the 'a pleasing' bit.
'lieutenant appearing about middle of film' is the wordplay.
'lieutenant' becomes 'lt' (abbreviation for lieutenant).
'appearing about' is an insertion indicator.
'middle of' indicates the central letters.
The centre of 'film' is 'il'.
'lt' enclosing 'il' is 'LILT'.
'has' acts as a link.
Can you help me to learn more?
(Other definitions for lilt that I've seen before include "Rise and fall" , "Sing happily" , "Tune with light pleasant rhythm" , "Light graceful swinging rhythm" , "Swing - rhythm" .)