With legs bent, run down and demand to be heard (5-5)
I believe the answer is:
knock-kneed
'with legs bent' is the definition.
(knock-kneed means having curved or bent legs)
'run down and demand to be heard' is the wordplay.
'run down' becomes 'knock' (both can mean to criticise or disparage).
'and' is a charade indicator (letters next to each other).
'demand' becomes 'need' (synonyms).
'to be heard' shows a homophone (sound like).
'need' is a homophone of 'kneed'.
'knock'+'kneed'='KNOCK-KNEED'
(Other definitions for knock-kneed that I've seen before include "Opposite of bow-legged" , "Opposite of bandy-legged?" , "With legs curving inwards" .)