It's an accomplishment with her light weight (7)
I believe the answer is:
feather
'light weight' is the definition.
Both the definition and answer are singular nouns.
Perhaps there's a link between them I don't understand?
'it's an accomplishment with her' is the wordplay.
'it's an accomplishment' becomes 'feat' (feat is a kind of accomplishment).
'with' is a charade indicator (letters next to each other).
'feat'+'her'='FEATHER'
Can you help me to learn more?
(Other definitions for feather that I've seen before include "'Birds of a . . . . . . . flock together'" , "trifling thing" , "Wing component" , "One of a bird's waterproof covering" , "English plume (de ma tante?)" .)