Starts to expect favours over time in sexual partner — save it for another time (8)
I believe the answer is:
leftover
'save it for another time' is the definition.
I can't tell whether this defines the answer.
'starts to expect favours over time in sexual partner' is the wordplay.
'starts to' says to take the initial letters.
'over' says to put letters next to each other.
'time' becomes 't' (abbreviation).
'in' means one lot of letters goes inside another.
'sexual partner' becomes 'lover' (I've seen this before. I am not sure about the 'sexual' bit.).
The first letters of 'expect favours' is 'ef'.
'ef'+'t'='eft'
'eft' put within 'lover' is 'LEFTOVER'.
Can you help me to learn more?
(Other definitions for leftover that I've seen before include "something you'd keep on the plate!" , "Remnant" , "Finally unused" , "What remains" , "Remaining" .)