This improved with right top (5)
I believe the answer is:
shirt
'top' is the definition.
(I know that shirt is a type of shirt)
'this improved with right' is the wordplay.
'improved with' is an anagram indicator.
'right' becomes 'r' (common abbreviation).
'this' mixed up with 'r' makes 'SHIRT'.
(Other definitions for shirt that I've seen before include "Man's garment" , "One may lose it at the bookie's" , "Garment for upper male body, usually cotton" , "Male garment worn with tie" , "tailored garment" .)