Act the soup-maker and keel over (4,6)
I believe the answer is:
turn turtle
'keel over' is the definition.
(both can mean to capsize as a boat)
'act the soup-maker' is the wordplay.
'act' becomes 'turn' (theatre).
'the soup-maker' becomes 'turtle' (a turtle may be used to make turtle soup).
'turn'+'turtle'='TURN TURTLE'
'and' is the link.
(Other definitions for turn turtle that I've seen before include "Tip over" , "(Of boat) invert" , "Capsize" , "Go over" , "Upend" .)