Party child loses footing — one to fall over? (6)
I believe the answer is:
domino
'loses footing one to fall over?' is the definition.
I can't judge whether this defines the answer.
'party child' is the wordplay.
'party' becomes 'do' (do is a kind of party).
'child' becomes 'mino' (I can't justify this - if you can you should give a lot more credence to this answer).
'do'+'mino'='DOMINO'
Can you help me to learn more?
(Other definitions for domino that I've seen before include "Playing piece; mask" , "Small block with dots for table game" , "Loose cloak; game piece" , "Spotted piece used in a table game" , "Black and white game tile" .)