Call on half-a-dozen to take a seat (5)
I believe the answer is:
visit
'call on' is the definition.
(synonyms)
'half-a-dozen to take a seat' is the wordplay.
'half-a-dozen' becomes 'vi' (Roman numerals for six).
'to take a seat' becomes 'sit' (sit down on a seat).
'vi'+'sit'='VISIT'
(Other definitions for visit that I've seen before include "Come to see" , "Call in to see, socially or on business" , "Drop in; frequent" , "Pay social call" , "Go and see (someone)" .)