Previously stuffed by United exactly when expected (2,3)
I believe the answer is:
on cue
'exactly when expected' is the definition.
(right on cue)
'previously stuffed by united' is the wordplay.
'previously' becomes 'once' (once means in the past).
'stuffed by' means one lot of letters goes inside another (stuff can mean to fill or insert into).
'united' becomes 'U' (as in Man U, English football team).
'once' going around 'u' is 'ON CUE'.
(Other definitions for on cue that I've seen before include "As a snooker player might be" , "When signal given" , "(Appearing) just when required" , "When expected" , "at the appropriate time" .)