End with overweight sweetheart (4)
I believe the answer is:
fate
'end' is the definition.
(thesaurus)
'with overweight sweetheart' is the wordplay.
'with' says to put letters next to each other.
'overweight' becomes 'fat' (I've seen this before).
'sweetheart' becomes 'e' (the heart/centre of 'sweet'**).
'fat' next to 'e' is 'FATE'.
(Other definitions for fate that I've seen before include "Predestination" , "Lady luck" , "Final issue" , "Lot -- doom" , "Destiny, kismet" .)