Tom’s ruined more than half (4)
I believe the answer is:
most
'more than half' is the definition.
(thesaurus)
'tom's ruined' is the wordplay.
'ruined' indicates anagramming the letters.
'toms' with letters rearranged gives 'MOST'.
(Other definitions for most that I've seen before include "Almost all" , "Nearly all, majority" , "Greatest in amount or degree" , "In the highest degree" , "Extremely, very" .)