Call on at six and pose (5)
I believe the answer is:
visit
'call on' is the definition.
(synonyms)
'six and pose' is the wordplay.
'six' becomes 'VI' (Roman numerals).
'and' is a charade indicator (letters next to each other).
'pose' becomes 'sit' (sitting is a kind of posing).
'vi'+'sit'='VISIT'
'at' acts as a link.
(Other definitions for visit that I've seen before include "Inflict" , "Call upon" , "Look up" , "Call in to see, socially or on business" , "Drop in; frequent" .)