The girl is different, having lost weight (7)
I believe the answer is:
lighter
'lost weight' is the definition.
The answer and definition can be both man-made objects as well as being singular nouns.
Perhaps they are linked in a way I don't understand?
'the girl is different' is the wordplay.
'is different' indicates an anagram (letters placed in a different order).
'the'+'girl'='thegirl'
'thegirl' is an anagram of 'LIGHTER'.
'having' is the link.
Can you help me to learn more?
(Other definitions for lighter that I've seen before include "Boat for heavy loads and fire igniter" , "relieved of some cargo?" , "Kind of barge - carrying less?" , "Barge; one needed by smoker" , "Canal boat with a flat bottom" .)