A solicitor with a vase in attendance (7)
I believe the answer is:
turnout
'attendance' is the definition.
(I know that turnout is a type of attendance)
'a solicitor with a vase' is the wordplay.
'a solicitor' becomes 'tout' (someone who solicits business).
'with' indicates putting letters inside.
'a vase' becomes 'urn' (both can mean a container).
'tout' enclosing 'urn' is 'TURNOUT'.
'in' acts as a link.
(Other definitions for turnout that I've seen before include "Eventuate; dismiss" , "Numbers attending an event" , "Number of people attending an event" , "Attendance figure" , "number of people coming to meeting" .)