Set in motion again on a filling meal (8)
I believe the answer is:
relaunch
'set in motion again' is the definition.
('launch' can be a synonym for 'set in motion' so perhaps 'relaunch' is OK for 'set in motion again')
'on a filling meal' is the wordplay.
'on' becomes 're' (regarding).
'filling' means one lot of letters goes inside another.
'meal' becomes 'lunch' (lunch is a kind of meal).
'a' inserted within 'lunch' is 'launch'.
're'+'launch'='RELAUNCH'
(Other definitions for relaunch that I've seen before include "Begin (enterprise) again" , "marketing operation" , "Again introduce" , "New introduction of old product" .)