Tom’s broken more than half (4)
I believe the answer is:
'more than half' is the definition.
(I've seen this in another clue)
'tom's broken' is the wordplay.
'broken' is an anagram indicator.
'toms' with letters rearranged gives 'MOST'.
(Other definitions for most that I've seen before include "Almost all" , "Nearly all, majority" , "Extremely, very" , "Kind of commercial pact where two countries agree to treat each other as well as any other" , "In the highest degree" .)